Samacheer Kalvi Class 10 Science Solutions Chapter 9 Solutions

I. Choose the Best Answer:

Question 1. A solution is a mixture.
(a) homogeneous
(b) heterogeneous
(c) homogeneous and heterogeneous
(d) non-homogeneous
Answer: (a) homogeneous
In simple words: A solution is a special type of mixture where everything is perfectly mixed and looks the same throughout, like sugar dissolved in water.

🎯 Exam Tip: Remember that "homogeneous" means uniform throughout, which is a key characteristic of true solutions.

Question 2. The number of components in a binary solution is ____.
(a) 2
(b) 3
(c) 4
(d) 5.
Answer: (a) 2
In simple words: A "binary" solution means it is made up of exactly two parts: a solute and a solvent. For example, sugar (solute) in water (solvent).

🎯 Exam Tip: "Bi-" always means two, so a binary solution always has two components. This helps remember the definition.

Question 3. Which of the following is the universal solvent?
(a) Acetone
(b) Benzene
(c) Water
(d) Alcohol
Answer: (c) Water
In simple words: Water is known as the "universal solvent" because it can dissolve more different substances than any other liquid. This is why it's so important for life!

🎯 Exam Tip: Water's ability to dissolve many substances is due to its polar nature and its ability to form hydrogen bonds.

Question 4. A solution in which no more solute can be dissolved in a definite amount of solvent at a given temperature is called ____.
(a) Saturated solution
(b) Unsaturated solution
(c) Supersaturated solution
(d) Dilute solution.
Answer: (a) Saturated solution
In simple words: A saturated solution is like a full sponge; it cannot hold any more solute. Any extra solute you add will just sit at the bottom.

🎯 Exam Tip: Understanding the difference between saturated, unsaturated, and supersaturated solutions is crucial. Saturated means maximum solute dissolved at a given temperature.

Question 5. Identify the non-aqueous solution.
(a) sodium chloride in water
(b) glucose in water
(c) copper sulphate in water
(d) sulphur in carbon-di-sulphide
Answer: (d) sulphur in carbon-di-sulphide
In simple words: A non-aqueous solution is one where the solvent is not water. In this case, carbon-di-sulphide is used instead of water to dissolve the sulphur.

🎯 Exam Tip: "Aqueous" means related to water. Therefore, "non-aqueous" means without water as the solvent.

Question 6. When pressure is increased at a constant temperature the solubility of gases in liquid ____.
(a) No change
(b) increases
(c) decreases
(d) no reaction.
Answer: (b) increases
In simple words: When you push harder on a gas above a liquid (increase pressure), more of that gas will dissolve into the liquid. This is why fizzy drinks are bottled under high pressure to keep the gas in.

🎯 Exam Tip: This principle is explained by Henry's Law, which states that the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid.

Question 7. Solubility of NaCl in 100 ml water is 36 g. If 25 g of salt is dissolved in 100 ml of water how much more salt is required for saturation:
(a) 12 g
(b) 11 g
(c) 16 g
(d) 20 g
Answer: (b) 11 g
In simple words: To make the salt solution completely full (saturated), you need 36 grams of salt. Since you already have 25 grams, you need 11 more grams to reach the maximum.

🎯 Exam Tip: Saturation means reaching the maximum amount of solute that can dissolve. Calculate the difference between the maximum solubility and the amount already dissolved.

Question 8. A 25% alcohol solution means ____.
(a) 25 ml of alcohol in 100 ml of water
(b) 25 ml of alcohol in 25 ml of water
(c) 25 ml of alcohol in 75 ml of water
(d) 75 ml of alcohol in 25 ml of water.
Answer: (c) 25 ml of alcohol in 75 ml of water
In simple words: A 25% solution means 25 parts of alcohol for every 100 parts of the total solution. So, 25 ml of alcohol mixed with 75 ml of water will give a total of 100 ml of solution.

🎯 Exam Tip: Percentage concentration is usually calculated as (amount of solute / total amount of solution) x 100. So, if the solution is 100ml total, 25ml is solute and 75ml is solvent.

Question 9. Deliquescence is due to:
(a) Strong affinity to water
(b) Less affinity to water
(c) Strong hatred to water
(d) Inertness to water
Answer: (a) Strong affinity to water
In simple words: Deliquescence happens when a substance loves water so much that it pulls moisture from the air and dissolves in it. It literally melts into its own absorbed water.

🎯 Exam Tip: Deliquescent substances absorb so much moisture that they actually turn into a liquid solution.

Question 10. Which of the following is hygroscopic in nature?
(a) ferric chloride
(b) copper sulphate pentahydrate
(c) silica gel
(d) none of the options.
Answer: (c) silica gel
In simple words: Silica gel is good at absorbing moisture from the air, but it does not dissolve in it. This property is why it is used in small packets to keep things dry.

🎯 Exam Tip: Hygroscopic substances absorb moisture but do not dissolve, while deliquescent substances absorb enough moisture to form a solution.

II. Fill in the Blanks:

Question 1. The component present in lesser amount, in a solution is called ____.
Answer: solute
In simple words: In any solution, the part that there is less of is called the solute. For example, in salt water, the salt is the solute.

🎯 Exam Tip: Always remember that the solvent is the component present in the larger amount, and it does the dissolving.

Question 2. Example for liquid in solid type solution is ____.
Answer: amalgam
In simple words: An amalgam is a special type of solution where a liquid (like mercury) is mixed into a solid (like silver) to form a new solid. Dental fillings used to be a common example.

🎯 Exam Tip: This question tests your knowledge of different types of solutions based on the physical states of solute and solvent.

Question 3. Solubility is the amount of solute dissolved in ____ g of solvent.
Answer: 100
In simple words: Solubility tells you how much of a substance can dissolve in a specific amount of solvent, usually measured in grams dissolved per 100 grams of solvent. This helps us compare how easily different things dissolve.

🎯 Exam Tip: Solubility is typically expressed as grams of solute per 100 g of solvent at a specific temperature, as temperature affects solubility.

Question 4. Polar compounds are soluble in ____ solvents.
Answer: Polar
In simple words: Substances that are "polar" (meaning they have slight positive and negative ends) tend to dissolve well in other "polar" liquids. This is often summed up as "like dissolves like."

🎯 Exam Tip: The principle "like dissolves like" is fundamental for understanding solubility. Polar solvents dissolve polar solutes, and non-polar solvents dissolve non-polar solutes.

Question 5. Volume percentage decreases with increases in temperature because ____.
Answer: of expansion of liquid
In simple words: When a liquid gets hotter, it usually expands and takes up more space. If the volume of the solution gets bigger because of this expansion, the calculated volume percentage of the solute will go down, even if the amount of solute stays the same.

🎯 Exam Tip: Temperature affects the volume of liquids due to thermal expansion, which in turn influences volume-based concentration terms like volume percentage.

III. Match the Following:

Question 1. Match the following:

🎯 Exam Tip: Memorize the common names and chemical formulas for these hydrated salts and understand the difference between deliquescent and hygroscopic substances.

IV. True or False: (If false give the correct statement):

Question 1. Solutions which contain three components are called binary solution.
Answer: False – Solutions which contain two components are called binary solution.
In simple words: A binary solution only has two parts (like sugar and water). If there are three parts, it is called a ternary solution.

🎯 Exam Tip: Pay attention to prefixes: "bi-" means two, "ter-" means three, "qua-" means four. These apply to the number of components in a solution.

Question 2. In a solution the component which is present in lesser amount is called solvent.
Answer: False – In a solution the component which is present in lesser amount is called solute.
In simple words: The component with the smaller amount is always the solute. The solvent is the one that dissolves the solute and is present in a larger amount.

🎯 Exam Tip: Clearly differentiate between solute and solvent. The solvent is typically the component in greater quantity and is responsible for dissolving the solute.

Question 3. Sodium chloride dissolved in water forms a non-aqueous solution.
Answer: False – Sodium chloride dissolved in water forms an aqueous solution.
In simple words: Since water is used as the solvent, the solution formed is called an aqueous solution. A non-aqueous solution uses a solvent other than water.

🎯 Exam Tip: Remember, any solution where water acts as the solvent is termed an aqueous solution. This is a common and basic definition.

Question 4. The molecular formula of green vitriol is \( \text{MgSO}_4 \cdot 7\text{H}_2\text{O} \)
Answer: False – The molecular formula of green vitriol is \( \text{FeSO}_4 \cdot 7\text{H}_2\text{O} \).
In simple words: Green vitriol is actually iron(II) sulfate heptahydrate. The formula \( \text{MgSO}_4 \cdot 7\text{H}_2\text{O} \) is for Epsom salt (magnesium sulfate heptahydrate), which is white, not green. Knowing this helps avoid confusion between similar chemical compounds.

🎯 Exam Tip: Be careful with the specific metal in hydrated salts; for instance, vitriol names (green, blue, white) are linked to different metal sulfates.

Question 5. When Silica gel is kept open, it absorbs moisture from the air, because it is hygroscopic in nature.
Answer: True
In simple words: Silica gel is very good at pulling moisture out of the air. This property is called being hygroscopic, and it means the substance absorbs water without dissolving.

🎯 Exam Tip: Hygroscopic substances are widely used as drying agents due to their ability to absorb atmospheric moisture.

V. Short Answer Questions:

Question 1. Define the term: Solution
Answer: A solution is a homogeneous mixture of two or more substances. For example, sugar dissolved in water creates a clear, uniform mixture.
In simple words: A solution is a perfectly mixed blend of two or more things that looks the same everywhere.

🎯 Exam Tip: The key terms here are "homogeneous mixture," meaning the components are uniformly distributed and cannot be easily distinguished.

Question 2. What is mean by the binary solution?
Answer: A binary solution is a solution that consists of exactly two components: one solute and one solvent. Such solutions are made up of just two distinct substances. For instance, when copper sulfate crystals are added to water, it forms a binary solution.
In simple words: A binary solution is simply a mix of two things, like one solute dissolving in one solvent.

🎯 Exam Tip: Emphasize the "two components" aspect in your definition of a binary solution. Using an example helps to illustrate the concept clearly.

Question 3. Give an example each
1. gas in liquid;
2. solid in liquid;
3. solid in solid;
4. gas in gas.
Answer:
1. Gas in liquid – \( \text{CO}_2 \) in water
2. Solid in liquid – NaCl in water
3. Solid in solid – Alloys
4. Gas in gas – He – \( \text{O}_2 \) gas
In simple words: Different kinds of solutions exist based on what mixes with what. For example, fizzy drinks have gas in liquid, saltwater has solid in liquid, metal alloys are solid in solid, and air is a mix of different gases.

🎯 Exam Tip: Provide clear and distinct examples for each type of solution to show a comprehensive understanding of physical states of solutes and solvents.

Question 4. What is the aqueous and non-aqueous solution? Give an example.
Answer:
An aqueous solution is a solution where water acts as the solvent. In general, ionic compounds dissolve easily in water to form aqueous solutions. Common salt (NaCl) in water is a good example of an aqueous solution.
A non-aqueous solution is a solution where any liquid other than water acts as the solvent. Alcohols, benzene, and ethers are commonly used as non-aqueous solvents. For instance, sulphur dissolved in carbon disulphide forms a non-aqueous solution.
In simple words: An aqueous solution uses water to dissolve things, like salt in water. A non-aqueous solution uses another liquid, like oil or alcohol, to dissolve things.

🎯 Exam Tip: Always clearly state the solvent when defining aqueous and non-aqueous solutions, and provide a distinct example for each.

Question 5. Define Volume percentage.
Answer: Volume percentage is defined as the percentage by volume of the solute (in ml) present in a given volume of the solution. It is often used for liquid-liquid solutions. The formula is:
\[ \text{Volume Percentage} = \frac{\text{Volume of the solute}}{\text{Volume of solute + Volume of solvent}} \times 100 \]
In simple words: Volume percentage tells you how much space the solute takes up compared to the total space of the solution, shown as a percentage.

🎯 Exam Tip: Ensure you differentiate between volume percentage (v/v) and mass percentage (w/w), and always remember to multiply by 100 for the percentage.

Question 6. The aquatic animals live more in a cold region. Why?
Answer: Aquatic animals live more in cold regions because the solubility of oxygen is higher in colder water, which means there is more dissolved oxygen available for them to breathe. Lower temperatures increase the amount of gas that can dissolve in water. Therefore, aquatic animals find it more comfortable to live in cold water as it provides them with more oxygen.
In simple words: Cold water holds more oxygen than warm water. So, aquatic animals prefer cold places because there is more oxygen for them to breathe easily.

🎯 Exam Tip: This question connects the concept of gas solubility with a real-world biological application. The key is understanding the inverse relationship between temperature and gas solubility in liquids.

Question 7. Define Hydrated salt.
Answer: Hydrated salts are ionic substances that crystallize out from their saturated aqueous solution with a definite number of water molecules chemically bonded within their crystal structure. These water molecules are called water of crystallization. For example, blue vitriol is a hydrated salt.
In simple words: Hydrated salts are solid chemicals that include a certain number of water molecules locked into their structure when they form crystals.

🎯 Exam Tip: The key characteristic of a hydrated salt is the "definite number of water molecules" in its crystal structure, often denoted with a dot in the chemical formula (e.g., \( \text{CuSO}_4 \cdot 5\text{H}_2\text{O} \)).

Question 8. A hot saturated solution of copper sulphate forms crystals as it cools. Why?
Answer: The ability of a solution to hold a specific amount of solute depends on temperature. When a hot saturated solution of copper sulphate cools down, its solubility decreases. This means the water can no longer hold all the dissolved copper sulphate. As a result, the solution becomes supersaturated, and the excess copper sulphate solute starts to separate out and form crystals. This process is called crystallization.
In simple words: When hot copper sulphate solution cools, it can't hold as much copper sulphate anymore. So, the extra copper sulphate comes out of the solution and turns into solid crystals.

🎯 Exam Tip: Most solid solubilities decrease with decreasing temperature. This phenomenon is fundamental to the process of crystallization, a common purification technique.

Question 9. Classify the following substances into deliquescent, hygroscopic. Cone. Sulphuric acid, Copper sulphate penta hydrate, Silica gel, Calcium chloride and Gypsum
Answer:

🎯 Exam Tip: Differentiate between deliquescent (absorbs enough water to dissolve and form a solution) and hygroscopic (absorbs water but does not dissolve) properties. Provide examples for each category.

VI. Long Answer Questions:

Question 1. Write notes on?
1. saturated solution
2. unsaturated solution
Answer:
1. Saturated solution: A saturated solution is a solution in which the maximum possible amount of solute has been dissolved in a definite amount of solvent at a specific temperature. If any more solute is added, it will not dissolve and will settle at the bottom. For example, 36 g of sodium chloride dissolved in 100 g of water at \( 25^\circ\text{C} \) forms a saturated solution. These solutions are at a state of dynamic equilibrium.
2. Unsaturated solution: An unsaturated solution is a solution that contains less solute than the maximum amount that can be dissolved in a definite amount of solvent at a specific temperature. In this solution, more solute can still be added and will dissolve. For example, 10 g, 20 g, or 30 g of sodium chloride dissolved in 100 g of water at \( 25^\circ\text{C} \) forms an unsaturated solution.
In simple words: A saturated solution has as much dissolved substance as it can hold, like a full cup. An unsaturated solution has less dissolved substance than it can hold, so you can still add more.

🎯 Exam Tip: When defining solution types, always mention the "definite amount of solvent" and "given temperature" as these conditions are crucial for their definitions.

Question 2. Write notes on various factors affecting solubility.
Answer: There are three main factors that influence the solubility of a solute:
1. Nature of the solute and solvent: The nature of both the solute and the solvent plays a significant role in solubility. Not all substances dissolve in water, even though it is a universal solvent. Dissolution occurs when there are similarities between the solute and the solvent; this is often summarized as "like dissolves like." For example, ionic compounds are typically soluble in polar solvents like water, while covalent compounds are soluble in non-polar solvents such as ether, benzene, or alcohol.
2. Effect of Temperature:
    Solubility of solid in liquid: Generally, the solubility of a solid solute in a liquid increases as the temperature increases. For endothermic processes (which absorb heat), solubility increases with temperature. For exothermic processes (which release heat), solubility decreases with increasing temperature. Many chemical reactions have a unique temperature dependence.
    Solubility of Gases in liquid: The solubility of gases in a liquid generally decreases as the temperature increases. This is why carbonated drinks go flat faster when warm.
3. Effect of Pressure: The effect of pressure is mainly observed in the solubility of a gas in a liquid. When the pressure above a liquid is increased, the solubility of the gas in that liquid also increases. This is described by Henry's Law, which explains why fizzy drinks are sealed under high pressure.
In simple words: How much a substance dissolves depends on three things: what kind of substance it is and what liquid it is trying to dissolve in, how hot or cold the liquid is, and how much pressure is pushing on it (especially for gases).

🎯 Exam Tip: When discussing factors affecting solubility, clearly explain the impact of each factor with specific examples and mention relevant laws like Henry's Law for gases.

Question 3. (a) What happens when \( \text{MgSO}_4 \cdot 7\text{H}_2\text{O} \) is heated? Write the appropriate equation (b) Define solubility.
Answer:
(a) When Epsom salt (\( \text{MgSO}_4 \cdot 7\text{H}_2\text{O} \)) crystals are gently heated, they lose their seven molecules of water of crystallization and turn into anhydrous magnesium sulfate (\( \text{MgSO}_4 \)), which is a white powder. This process is a dehydration reaction.
\[ \text{MgSO}_4 \cdot 7\text{H}_2\text{O} \xrightarrow{\text{heating}} \text{MgSO}_4 + 7\text{H}_2\text{O} \]
(b) Solubility is defined as the maximum amount of solute (in grams) that can be dissolved in 100 g of the solvent to form a saturated solution at a given temperature and pressure. It is a measure of how easily a substance dissolves.
In simple words: (a) When Epsom salt is heated, it loses its water and becomes a dry powder. (b) Solubility means how much of a substance can dissolve in a set amount of liquid at a certain temperature and pressure.

🎯 Exam Tip: For chemical reactions, always write a balanced equation and label reactants/products clearly. For definitions, ensure all key conditions (temperature, pressure, amount of solvent) are included.

Question 4. In what way hygroscopic substances differ from deliquescent substances.
Answer:

🎯 Exam Tip: Presenting differences in a table format makes the comparison clear and easy to understand. Focus on the key distinction: whether or not the substance dissolves to form a liquid.

Question 5. A solution is prepared by dissolving 45 g of sugar in 180 g of water. Calculate the mass percentage of solute.
Answer:
Mass of the solute (sugar) = 45 g
Mass of the solvent (Water) = 180 g
Formula for mass percentage of solute:
\[ \text{Mass percentage (W/W)} = \frac{\text{Mass of the solute}}{\text{Mass of the solute + Mass of the solvent}} \times 100 \]
Substitute the given values into the formula:
\[ \text{Mass percentage (sugar)} = \frac{45}{45 + 180} \times 100 \]
\[ = \frac{45}{225} \times 100 \]
\[ = 0.2 \times 100 \]
\[ = 20\% \]
The mass percentage of solute (sugar) = 20%. This calculation shows that sugar makes up 20% of the total mass of the solution.
In simple words: To find the mass percentage, you take the mass of the sugar, divide it by the total mass of the sugar and water together, and then multiply by 100. This tells you what percentage of the solution is sugar.

🎯 Exam Tip: Always ensure you use the total mass of the solution (solute + solvent) in the denominator when calculating mass percentage, not just the mass of the solvent.

Question 6. 3.5 litres of ethanol is present in 15 litres of aqueous solution of ethanol. Calculate volume percent of ethanol solution.
Answer:
Volume of ethanol (solute) = 3.5 litres = 3500 ml
Volume of water (solvent) = 15 litres = 15000 ml
First, calculate the total volume of the solution:
Total volume of solution = Volume of ethanol + Volume of water
Total volume of solution = 3500 ml + 15000 ml = 18500 ml
Formula for volume percentage:
\[ \text{Volume Percentage (V/V)} = \frac{\text{Volume of the solute (ml)}}{\text{Volume of the solution (ml)}} \times 100 \]
Substitute the values into the formula:
\[ \text{Volume Percentage} = \frac{3500}{18500} \times 100 \]
\[ = 0.189189... \times 100 \]
\[ = 18.92\% \]
The volume percentage of ethanol solution is approximately 18.92%. This means that 18.92% of the solution's volume is ethanol.
In simple words: To find the volume percentage, divide the amount of ethanol by the total amount of the liquid mixture, then multiply by 100. Remember to add the volumes of ethanol and water to get the total volume.

🎯 Exam Tip: Ensure that both the solute and solution volumes are in the same units (e.g., ml). Carefully distinguish between the volume of solvent and the total volume of the solution.

VII. HOT Questions

Question 1. Vinu dissolves 50 g of sugar in 250 ml of hot water, Sarath dissolves 50 g of same sugar in 250 ml of cold water. Who will get a faster dissolution of sugar? and Why?
Answer: Vinu will achieve a faster dissolution of sugar. This is because, for most solid solutes like sugar, solubility in a liquid solvent generally increases with an increase in temperature. Hot water molecules move faster and have more energy, allowing them to break apart the sugar crystals more quickly and spread the sugar molecules throughout the water more efficiently. Therefore, Vinu's sugar will dissolve more rapidly than Sarath's.
In simple words: Vinu's sugar will dissolve faster because hot water helps sugar dissolve more quickly. Hot water makes the water molecules move faster, breaking up the sugar crystals quicker.

🎯 Exam Tip: When explaining solubility factors, always link the observation (faster dissolution) to the underlying scientific principle (increased kinetic energy of solvent molecules at higher temperatures).

Question 2. 'A' is a blue coloured crystalline salt. On heating it loses blue colour and to give 'B' When water is added, 'B' gives back to 'A'. Identify A and B, write the equation.
Answer:
'A' is a blue coloured crystalline salt, which is Copper(II) sulfate pentahydrate, \( \text{CuSO}_4 \cdot 5\text{H}_2\text{O} \) (also known as Blue vitriol).
When \( \text{CuSO}_4 \cdot 5\text{H}_2\text{O} \) is heated, it loses all five water molecules of crystallization and becomes 'B', a colourless anhydrous copper sulfate, \( \text{CuSO}_4 \). Anhydrous means "without water".
The equation for heating is:
\[ \text{CuSO}_4 \cdot 5\text{H}_2\text{O} \xrightarrow{\text{heating}} \text{CuSO}_4 + 5\text{H}_2\text{O} \]
When water is added to 'B' (anhydrous \( \text{CuSO}_4 \)), it re-absorbs the water and turns back into blue crystalline 'A' (\( \text{CuSO}_4 \cdot 5\text{H}_2\text{O} \)). This reaction is often used to test for water.
In simple words: 'A' is blue copper sulfate with water inside it. When heated, it loses the water, turns white, and becomes 'B'. When you add water back to 'B', it turns blue again. This change helps us spot when water is present.

🎯 Exam Tip: This is a classic example of a dehydration and rehydration reaction, often used to demonstrate the presence of water in hydrated salts. Memorize the formula and color changes.

Question 3. Will the cool drinks give more fizz at top of the hills or at the foot? Explain.
Answer: The cool drinks will give more fizz at the foot of the hills, and less fizz at the top of the hills. This is because fizz in cool drinks comes from dissolved carbon dioxide gas. According to Henry's Law, the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid. At the top of the hills, the atmospheric pressure is lower than at the foot. With lower pressure, less carbon dioxide can remain dissolved in the drink, so more gas escapes, resulting in less fizz when opened. Conversely, at the foot of the hills, the pressure is higher, allowing more carbon dioxide to stay dissolved, leading to more fizz upon opening.
In simple words: Cool drinks fizz more at the bottom of a hill than at the top. This is because there is more air pressure at the bottom, which helps keep the fizz (carbon dioxide gas) inside the drink. Less pressure at the top means the gas escapes more easily.

🎯 Exam Tip: Relate the concept to Henry's Law and the effect of atmospheric pressure on gas solubility. A higher elevation means lower atmospheric pressure.

Samacheer Kalvi 10th Science Solutions Additional Important Questions and Answers

I. Choose the Correct Answer:

Question 1. The dissolution of sugar and salt in water results in a solution.
(a) Binary
(b) Ternary
(c) Quaternary
(d) Saturated
Answer: (b) Ternary
In simple words: If you dissolve both sugar and salt in water, you have three different parts: sugar, salt, and water. A solution with three parts is called a ternary solution.

🎯 Exam Tip: Count the distinct components: sugar, salt, and water make three. So, it's a ternary solution.

Question 2. In a solution, the component which is present in a lesser amount is called ____.
(a) solvent
(b) dissolution
(c) solute
(d) mole.
Answer: (c) solute
In simple words: The smaller part in a solution that gets dissolved is always called the solute. For example, sugar in sugar water is the solute.

🎯 Exam Tip: This is a fundamental definition. The component in the larger amount is the solvent, and the one in the lesser amount is the solute.

Question 3. The supersaturated solution of NaCl in 100 g of water at \( 25^\circ\text{C} \) contains:
(a) 40 g of NaCl
(b) 10 g of NaCl
(c) 20 g of NaCl
(d) 30 g of NaCl
Answer: (a) 40 g of NaCl
In simple words: A supersaturated solution means it holds more dissolved salt than it normally should at that temperature. Since a saturated solution can hold 36 g, 40 g means it is supersaturated.

🎯 Exam Tip: Recall that the solubility of NaCl in 100 g water at \( 25^\circ\text{C} \) is 36 g. A supersaturated solution exceeds this amount.

Question 4. How many component(s) present in binary solution?
(a) 1
(b) 2
(c) 3
(d) 4.
Answer: (b) 2
In simple words: A "binary" solution, by definition, always has exactly two parts. "Bi" means two.

🎯 Exam Tip: Understand the prefixes: 'bi-' for two, 'tri-' for three, 'quad-' for four. This applies universally to chemical terminology regarding components.

Question 5. Formalin is an aqueous solution of:
(a) formic acid
(b) ammonia
(c) formaldehyde
(d) carbon tetrachloride
Answer: (c) formaldehyde
In simple words: Formalin is a specific type of solution where formaldehyde gas is dissolved in water. It is commonly used as a preservative.

🎯 Exam Tip: Remember that "aqueous solution" means a solution where water is the solvent. Formalin is an important chemical for preservation.

Question 6. The effect of pressure on the solubility of a gas in liquids is given by:
(a) Boyle's Law
(b) Charles' Law
(c) Henry's Law
(d) Avogadro's Law
Answer: (c) Henry's Law
In simple words: Henry's Law explains how more gas dissolves in a liquid when you increase the pressure above it. Think of how soda stays fizzy until you open the bottle.

🎯 Exam Tip: Clearly distinguish between gas laws like Boyle's and Charles' Law (which deal with gas properties) and Henry's Law (which specifically addresses gas solubility in liquids).

Question 7. Which one of the following is an example of an aqueous solution?
(a) Sugar in water
(b) Sulphur in carbon disulphide
(c) Iodine dissolved in carbon tetrachloride
(d) Benzoic acid in ethers.
Answer: (a) Sugar in water
In simple words: An aqueous solution means water is used as the dissolving liquid (solvent). Sugar dissolves well in water, making it a common aqueous solution.

🎯 Exam Tip: Always identify the solvent to determine if a solution is aqueous (water is solvent) or non-aqueous (another liquid is solvent).

Question 8. The type of solution when \( CO_2 \) is dissolved in water:
(a) solid/liquid
(b) liquid in liquid
(c) gas in liquid
(d) liquid in solid
Answer: (c) gas in liquid
In simple words: When you have carbon dioxide gas mixed into water, which is a liquid, you get a gas-in-liquid solution. This is how fizzy drinks are made.

🎯 Exam Tip: Classify solutions by the physical state of the solute first, then the solvent. Carbon dioxide is a gas, and water is a liquid.

Question 9. Tin amalgam is an example of ......... solution.
(a) solid in solid
(b) liquid in solid
(c) solid in liquid
(d) liquid in liquid
Answer: (b) liquid in solid
In simple words: An amalgam is a special type of mixture where mercury (a liquid metal) is combined with another metal (a solid). So, tin amalgam means liquid mercury is mixed into solid tin.

🎯 Exam Tip: Remember that amalgam refers to solutions where one component is mercury. Its state (liquid) determines the solution type if the other component is solid.

Question 10. In which case solubility decreases with increase in temperature?
(a) Endothermic process
(b) Exothermic process
(c) Both (a) and (b)
(d) None of the options
Answer: (b) Exothermic process
In simple words: For a process that releases heat (exothermic), making it hotter actually makes less of the substance dissolve. It's like the system wants to cool down, so adding more heat works against dissolving.

🎯 Exam Tip: Generally, solubility increases with temperature for endothermic processes (heat absorbed) and decreases for exothermic processes (heat released).

Question 11. Fat is soluble in:
(a) water
(b) alcohol
(c) \( CCl_4 \)
(d) ether
Answer: (d) ether
In simple words: Fats are non-polar substances, and they dissolve well in other non-polar solvents like ether. This is because "like dissolves like".

🎯 Exam Tip: The principle "like dissolves like" is key here: polar substances dissolve in polar solvents, and non-polar substances dissolve in non-polar solvents.

Question 12. The deliquescent substance among the following is:
(a) con. \( H_2SO_4 \)
(b) \( P_2O_5 \)
(c) \( CaCl_2 \)
(d) \( SiO_2 \)
Answer: (c) \( CaCl_2 \)
In simple words: Calcium chloride is a substance that absorbs a lot of moisture from the air and eventually dissolves in it to form a solution. This property is called deliquescence.

🎯 Exam Tip: Deliquescent substances absorb so much moisture from the air that they form a solution, while hygroscopic substances only absorb moisture without dissolving.

Question 13. Mass percentage is expressed as _____.
(a) v/v
(b) w/w
(c) w/v
(d) v/w.
Answer: (b) w/w
In simple words: Mass percentage is about how much mass of a substance is in the total mass of the mixture. So, it's measured as weight (w) by weight (w).

🎯 Exam Tip: Understand the abbreviations: 'w' stands for weight/mass, and 'v' stands for volume. Mass percentage is always (mass of solute / mass of solution) x 100.

Question 14. Hygroscopic substances are used as ......... agents.
(a) foaming
(b) drying
(c) oxidising
(d) reducing
Answer: (b) drying
In simple words: Hygroscopic substances are good at pulling moisture out of the air. Because of this, they are often used to dry things or keep moisture away from sensitive items.

🎯 Exam Tip: A drying agent is also known as a desiccant. This property is due to their strong affinity for water molecules.

Question 15. The molecular formula of Epsom salt is _____.
(a) \( CuSO_4.5H_2O \)
(b) \( FeSO_4.7H_2O \)
(c) \( MgSO_4.7H_2O \)
(d) \( ZnSO_4.7H_2O \).
Answer: (c) \( MgSO_4.7H_2O \)
In simple words: Epsom salt is actually magnesium sulfate heptahydrate, meaning it has seven water molecules attached to each magnesium sulfate unit. It's often used in bath salts.

🎯 Exam Tip: Hydrated salts have specific numbers of water molecules associated with their crystal structure, indicated by the dot formula.

II. Fill in the blanks:
Answer:
1. A true solution is a homogeneous mixture of solute and solvent. 2. Soil cannot store more nitrogen than it can hold because soil is said to be in a state of saturation. 3. In the dissolution of NaOH in water, the solubility decreases with increase in temperature. 4. Aquatic animals are more comfortable in cold water because as the temperature is less the solubility of dissolved oxygen increases. 5. Hydrated salts contain water of crystallization. 6. He-\( O_2 \) mixture is a binary solution of Gas in Gas solution. 7. The solvent used for dissolving Sulphur is \( CS_2 \) (or) Carbon disulphide. 8. The solubility of NaOH at \( 25^\circ C \) is 80 g. 9. According to Henry's Law, the solubility of a gas in liquid is directly proportional to the pressure of the gas over the solution at definite temperature. 10. Anhydrous Calcium chloride is a Hygroscopic substance. 11. Deliquescent substances absorb enough water from the atmosphere and get completely dissolved. 12. When 90g of sodium bromide is dissolved in 100 g of water at \( 25^\circ C \) it forms a Unsaturated solution. 13. Cloud is an example of a binary solution with liquid in Gas. 14. Air and sea water are important Homogeneous solution. 15. A quaternary solution contains four components. 16. The primary factor which determines the characteristic of a solution is Physical state.
In simple words: These blanks cover key terms and concepts about solutions, including types of mixtures, solubility factors like temperature and pressure, and characteristics of different substances. Filling them helps you remember the main ideas.

🎯 Exam Tip: For fill-in-the-blank questions, ensure you understand the core definition or principle being tested. Review terms like homogeneous, saturation, hygroscopic, and deliquescent.

III. Match the following

Question 1. Match the column I with column II.

🎯 Exam Tip: Practice classifying solutions based on the physical state of their components. Alloys are solid-solid, amalgams are liquid-solid, and ethyl alcohol in water is liquid-liquid.

Question 2. Match the column I with column II.

🎯 Exam Tip: Understand the characteristics of different solution types: gas in gas, solvent for non-polar substances, and the nature of supersaturated and dilute solutions.

Question 3. Match the column I with column II.

🎯 Exam Tip: Pay attention to the precise definitions and chemical formulas. Henry's Law is specifically for gases in liquids, and gypsum has a characteristic hydration number.

Question 4. Match the column I with column II.

🎯 Exam Tip: Pay close attention to the definition of deliquescence, the specific hydration of vitriols, and the role of different solvents.

IV. True or False: (If false give the correct statement)
Answer:
1. False – In an aqueous solution of copper sulphate, the solvent is water.
2. False – A solution containing sugar and salt in water is a ternary solution.
3. True
4. True
5. True
6. False – Fat is dissolved in the non-aqueous solvent ether.
7. False – The solubility of a gas in a liquid is directly proportional to the pressure of the gas at a definite temperature.
8. True
9. True
10. False – Ferric chloride is a deliquescent substance.
In simple words: This section checks your basic understanding of solution properties, terms like aqueous and ternary, and the behavior of substances regarding solubility and moisture absorption. Remember to correct false statements with accurate information.

🎯 Exam Tip: When correcting false statements, ensure your explanation is precise and directly addresses the incorrect part of the original statement.

V. Short answer questions:

Question 1.
(i) Which gas is dissolved in soft drinks?
(ii) What will you do to increase the solubility of this gas?
Answer:
(i) Carbon-di-oxide (\( CO_2 \)) is dissolved in soft drinks.
(ii) An increase in pressure will increase the solubility of \( CO_2 \) gas. Also, lowering the temperature makes more gas dissolve.
In simple words: Fizzy drinks contain carbon dioxide gas. To make more of this gas dissolve, you need to add more pressure and keep the drink cold.

🎯 Exam Tip: Remember Henry's Law states that gas solubility increases with pressure. For most gases, solubility also increases with decreasing temperature.

Question 2. Identify the type of binary solution for each of the following examples:
1. Alloys
2. Amalgam
3. Ethyl alcohol in water
4. Aerated drinks
Answer:
1. Alloys: Solid in solid
2. Amalgam: Liquid in solid
3. Ethyl alcohol in water: Liquid in liquid
4. Aerated drinks: Gas in liquid
In simple words: This lists common examples and tells you what kind of mixture they are, based on if the main parts are solid, liquid, or gas. For example, an alloy is a mix of two solids.

🎯 Exam Tip: To classify solutions, identify the physical state of the solute (the substance being dissolved) and the solvent (the substance doing the dissolving).

Question 3. Explain why Nitrogen in soil is called a saturated solution in nature?
Answer: Nitrogen in soil is considered a saturated solution in nature because the soil can only hold a certain maximum amount of nitrogen. Once this limit is reached, no more nitrogen can be absorbed, even if more is available. This balance prevents the soil from becoming overloaded with nitrogen.
In simple words: Nitrogen in soil is like a full sponge; it can only hold a limited amount, so it's called a saturated solution because it can't take in any more.

🎯 Exam Tip: A saturated solution is one where the maximum amount of solute has dissolved in a given solvent at a specific temperature, with no more being able to dissolve.

Question 4. Define Mass percentage.
Answer: Mass percentage of a solution is defined as the percentage by mass of the solute present in the solution. It tells you the proportion of a component by mass.
\[ \text{Mass Percentage} = \frac{\text{Mass of the solute}}{\text{Mass of the solute} + \text{Mass of the solvent}} \times 100 \]
In simple words: Mass percentage tells you what part of a mixture's total weight comes from a specific ingredient, shown as a percentage.

🎯 Exam Tip: The denominator in mass percentage is always the total mass of the solution (solute + solvent), not just the solvent.

Question 5. Define the term Molarity (M).
Answer: Molarity (M) is a way to measure the concentration of a solution. It is defined as the number of moles of solute present in one liter of the solution. This measure is temperature-dependent because volume changes with temperature.
\[ \text{Molarity (M)} = \frac{\text{No. of moles of the solute}}{\text{Volume of the solution in Lit}} \]
In simple words: Molarity tells you how many "moles" of a substance are mixed into one liter of a liquid. It's a way to measure how strong a solution is.

🎯 Exam Tip: Molarity uses the volume of the *solution*, not just the solvent, and the volume must be in liters.

Question 6. Define the term Molality (m).
Answer: Molality (m) is a measure of concentration that describes the number of moles of solute dissolved in one kilogram of the solvent. Unlike molarity, molality is independent of temperature because it uses mass, which doesn't change with temperature.
\[ \text{Molality (m)} = \frac{\text{No. of moles of the solute}}{\text{Mass of solvent in Kg}} \]
In simple words: Molality measures how many "moles" of a substance are mixed into one kilogram of the dissolving liquid. It is useful because it doesn't change with temperature.

🎯 Exam Tip: Remember the key difference: Molarity uses volume of solution, while Molality uses mass of *solvent* (in kg).

Question 7. Define the supersaturated solution.
Answer: A supersaturated solution is a special type of solution that contains more solute than what can normally be dissolved in a given amount of solvent at a specific temperature. These solutions are usually unstable and can cause the extra solute to crystallize out if disturbed. For example, 40 g of sodium chloride in 100 g of water at \( 25^\circ C \) would be supersaturated if the normal saturation limit is less.
In simple words: A supersaturated solution has more of a substance dissolved in it than it normally should. It is very tricky and can easily make the extra substance turn back into solid crystals.

🎯 Exam Tip: Supersaturated solutions are prepared by dissolving a solute at a higher temperature and then carefully cooling the solution without crystallization.

Question 8. Justify the following statements with an explanation.
(i) Solubility of \( NH_4Cl \) increases with increase in temperature.
(ii) Solubility of NaOH decreases with increase in temperature.
Answer:
(i) Solubility of \( NH_4Cl \) increases with an increase in temperature because its dissolution is an endothermic process. This means it absorbs heat from its surroundings as it dissolves, so adding more heat (increasing temperature) helps it dissolve even more.
(ii) Solubility of NaOH decreases with an increase in temperature because its dissolution is an exothermic process. This means it releases heat when it dissolves, so increasing the temperature actually works against its tendency to dissolve. The system tries to reduce the added heat by dissolving less.
In simple words: Some things dissolve more when it's hotter because they use up heat (like \( NH_4Cl \)), while other things dissolve less when it's hotter because they give off heat (like NaOH).

🎯 Exam Tip: Link the change in solubility with temperature to the enthalpy of solution. Endothermic dissolution (absorbs heat) favors higher temperatures, while exothermic dissolution (releases heat) favors lower temperatures.

Question 9. Calculate the molarity of a solution containing 4 g of NaOH in 500 ml of water.
Answer:
Mass of NaOH \( = 4 \, \text{g} \)
Volume of solution \( = 500 \, \text{ml} \)
To find molarity, we first need the number of moles of NaOH.
Molecular mass of NaOH \( = 23 (Na) + 16 (O) + 1 (H) = 40 \, \text{g/mol} \)
No. of moles of NaOH \( = \frac{\text{Given mass}}{\text{Mol. mass}} = \frac{4}{40} = 0.1 \, \text{mol} \)
Next, convert the volume to liters: Volume \( = 500 \, \text{ml} = 0.5 \, \text{Lit} \)
Now, calculate Molarity:
\[ \text{Molarity (M)} = \frac{\text{No. of moles of the solute}}{\text{Volume of the solution in Lit}} \]
\[ \text{Molarity (M)} = \frac{0.1}{0.5} = 0.2 \, \text{M} \] Therefore, the molarity of the solution is 0.2 M. This tells us the concentration of the sodium hydroxide.
In simple words: First, find how many "moles" of NaOH you have. Then, divide that number by the total volume of the liquid in liters to get the molarity, which shows how concentrated the solution is.

🎯 Exam Tip: Always ensure the volume is in liters when calculating molarity. Double-check your calculation of molecular mass for the solute.

Question 10. Calculate the molality of a solution containing 3 g of urea (molecular mass = 60) in 750 g of water.
Answer:
Mass of urea (solute) \( = 3 \, \text{g} \)
Molecular mass of urea \( = 60 \, \text{g/mol} \)
Mass of water (solvent) \( = 750 \, \text{g} \)
First, find the number of moles of urea:
No. of moles of urea \( = \frac{\text{Given mass}}{\text{Mol. mass}} = \frac{3}{60} = 0.05 \, \text{mol} \)
Next, convert the mass of solvent to kilograms:
Mass of solvent \( = 750 \, \text{g} = 0.750 \, \text{kg} \)
Now, calculate Molality:
\[ \text{Molality (m)} = \frac{\text{No. of moles of the solute}}{\text{Mass of solvent in Kg}} \]
\[ \text{Molality (m)} = \frac{0.05}{0.750} \approx 0.067 \, \text{m} \] Therefore, the molality of the solution is approximately 0.067 m. Molality is a useful measure for properties that depend on solute-solvent interactions.
In simple words: To find molality, first figure out how many "moles" of urea you have. Then, divide that by the weight of the water in kilograms. This tells you how strong the solution is based on weight, not volume.

🎯 Exam Tip: For molality, the mass of the solvent must be in kilograms, and it's the solvent's mass, not the total solution's mass.

Question 11. Define dissolution.
Answer: Dissolution is the process where a solute (like sugar) mixes uniformly into a solvent (like water) to form a homogeneous solution. During this process, the particles of the solute separate and get surrounded by the particles of the solvent. This is a fundamental step in making any solution.
In simple words: Dissolution is when one substance completely breaks apart and spreads evenly into another liquid, making a uniform mixture.

🎯 Exam Tip: Emphasize "uniform distribution" and "homogeneous solution" when defining dissolution to get full marks.

VI. Long answer questions:

Question 1. Answer the blanks given in the table.
Answer:

🎯 Exam Tip: Understanding the physical states of solute and solvent is crucial for classifying different types of solutions correctly.

Question 2. Write a note on the type of solution based on the type of solvent.
(i) Aqueous solution
(ii) Non-Aqueous solution
Answer:
(i) Aqueous solution: An aqueous solution is a solution where water acts as the solvent. In simple terms, anything dissolved in water forms an aqueous solution. Generally, ionic compounds like common salt, sugar, and copper sulphate are highly soluble in water and form aqueous solutions more easily than covalent compounds.
(ii) Non-Aqueous solution: A non-aqueous solution is one where any liquid other than water acts as the solvent. These are used when the solute does not dissolve in water or reacts with it. Common non-aqueous solvents include alcohols, benzene, ethers, carbon disulphide, and acetone. For example, sulphur dissolved in carbon disulphide, or iodine dissolved in carbon tetrachloride, are non-aqueous solutions.
In simple words: Solutions are either "aqueous" if water is the main dissolving liquid, or "non-aqueous" if any other liquid is used to dissolve something. Water dissolves many things, but not everything.

🎯 Exam Tip: Clearly state that water is the solvent for aqueous solutions and any other liquid is the solvent for non-aqueous solutions, providing distinct examples for each.

Question 3. Justify the following statements with an explanation.
1. The solubility of calcium oxide decreases with increase in temperature,
2. What happens to the solubility in the exothermic process with regard to temperature?
3. In the endothermic process, solubility increases with increase in temperature.
4. At a given temperature, an increase in pressure increases the solubility of the gas
Answer:
1. The solubility of calcium oxide decreases with an increase in temperature because its dissolution in water is an exothermic process. This means it releases heat, so adding more heat shifts the balance to favor less dissolving.
2. In an exothermic process, solubility generally decreases as temperature increases. This is because the process already releases heat, so adding more heat from the outside pushes the equilibrium to dissolve less of the solute.
3. In an endothermic process, solubility generally increases as temperature increases. This happens because the process absorbs heat, so providing more heat by increasing the temperature helps more of the solute dissolve.
4. At a given temperature, an increase in pressure increases the solubility of a gas in a liquid. This is explained by Henry's Law, which states that more gas molecules are forced into the liquid phase when the external pressure is higher. This is why carbon dioxide stays dissolved in soft drinks until the bottle is opened.
In simple words: For things that give off heat when they dissolve, warming them makes them dissolve less. For things that need heat to dissolve, warming them makes them dissolve more. And for gases, more pressure means more gas can dissolve in a liquid.

🎯 Exam Tip: Always relate solubility changes with temperature to whether the dissolution process is endothermic (heat absorbed) or exothermic (heat released), and connect gas solubility to Henry's Law.

VII. Hot Questions.

Question 1. 50 ml tincture of benzoin, antiseptic solution contains 10 ml of benzoin. Calculate the volume of percentage of benzoin.
Answer:
Volume of the solute (Benzoin) \( = 10 \, \text{ml} \)
Volume of the solution (tincture of benzoin) \( = 50 \, \text{ml} \)
To calculate the volume percentage (V/V):
\[ \text{Volume percentage (V/V)} = \frac{\text{Volume of solute (in ml)}}{\text{Volume of solution (in ml)}} \times 100 \]
\[ \text{Volume percentage (V/V)} = \frac{10}{50} \times 100 \]
\[ = 0.2 \times 100 = 20\% \] Therefore, the volume percentage of benzoin in the solution is 20%. This calculation is straightforward when the volumes are given directly.
In simple words: To find the volume percentage, you divide the volume of the substance you're interested in (benzoin) by the total volume of the mixture, then multiply by 100.

🎯 Exam Tip: Remember that volume percentage calculations require both the solute and solution volumes to be in the same units, typically milliliters.

VIII. Numerical Problems:

Question 1. Calculate the molality of the solution containing 18 g of urea (molecular mass = 60) in 2 kg of water.
Answer:
Mass of Glucose \( = 18 \text{ g} \)
Molecular mass of Glucose \( = 180 \)
No. of moles of solute \( = \frac { 18 }{ 180 } = 0.1 \text{ mol} \)
Mass of solvent (water) \( = 2 \text{ kg} \)
Molality \( = \frac{ \text{No. of moles of solute} }{ \text{Mass of solvent (in kg)} } \)
Molality \( = \frac{ 0.1 }{ 2 } \)
Molality \( = 0.05 \text{ m} \)
This molality value tells us that for every kilogram of water, there are 0.05 moles of glucose dissolved, showing the solution's concentration clearly.
In simple words: First, we figure out how many moles of glucose are present by dividing its weight by its molecular weight. Then, we divide this number by the weight of water in kilograms to find the molality, which shows how concentrated the solution is.

🎯 Exam Tip: Remember to use the mass of the solvent (not the solution) in kilograms when calculating molality. Pay attention to whether the problem gives the molecular mass for the substance mentioned.

Question 2. Calculate the molarity of a solution containing 5.85 g of sodium chloride in 500 ml of the water. (Molecular mass = 58.5)
Answer:
Mass of the solute \( = 5.85 \text{ g} \)
Volume of the solution \( = 500 \text{ ml} \)
Molecular mass \( = 58.5 \)
No. of moles of NaCl \( = \frac{ 5.85 }{ 58.5 } = 0.1 \)
Molarity \( = \frac{ \text{No. of moles of the solute} }{ \text{Volume of solution in Lit} } \)
Since \( 500 \text{ ml} = 0.5 \text{ Lit} \)
Molarity \( = \frac{ 0.1 }{ 0.5 } \)
Molarity \( = 0.2 \text{ M} \)
This calculation shows that there are 0.2 moles of sodium chloride in every liter of the solution, giving a precise measure of its concentration.
In simple words: We first find the moles of salt by dividing its mass by its molecular weight. Then, we divide these moles by the solution's volume (in liters) to get the molarity, which tells us how much salt is dissolved per liter.

🎯 Exam Tip: Always convert the volume to liters when calculating molarity, even if it's given in milliliters. Use the molecular mass correctly to find the number of moles.