CBSE Class 10 Chemistry Acids Base and Salts Worksheet Set D

CBSE Class 10 Chemistry Acids Base and Salts Worksheet Set D

Assertion and Reason Type MCQs :

Following questions consists of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below:
A. Both assertion and reason are true, and reason is the correct explanation of assertion.
B. Both assertion and reason are true, but reason is not the correct explanation of assertion.
C. Assertion is true but reason is false.
D. Assertion is false and reason is true.

Question. Assertion (A): When dil. H₂SO₄ is added to zinc granules, a physical change is observed.
Reason(R): A gas is evolved which burns with ‘pop’ sound.

Answer: D

Question. Assertion (A): pH = 7 indicates pure water.
Reason(R): At the pH 7, [H⁺] = [OH^-] = 10^-7

Answer: D

Question. Assertion(A): The chemical formula of bleaching powder is CaOCl₂.
Reason(R): Chlorine gas is passed over Calcium Oxide to form bleaching powder.

Answer: A

Question. Assertion(A): NaHCO₃+ HCl = NaCl + H₂O + CO₂
Reason (R): Evolved gas catches fire immediately.

Answer: C

Question. Assertion(A): Plaster of Paris is stored in moisture proof containers.
Reason(R) : Plaster of Paris sets into a hard mass on coming in contact with water to form anhydrous Calcium Sulphate.

Answer: C

Question. Assertion(A): NH4Cl is an acidic salt.
Reason(R): NH4Cl is the salt of hydrochloric acid and ammonium hydroxide.

Answer: A

Question. Assertion(R): The compound prepared from gypsum on heating it at 373 K , is known as Plaster of Paris.
Reason(R): Plaster of Paris is used in hospitals mainly as plaster for supporting fractured bones in the right position. In dentistry, it is used for making casts.

Answer: B

Question. Assertion(A): Bleaching powder is CaOCl₂, and is prepared from chlorine and slaked lime
Reason(R): Bleaching powder can be used for bleaching, disinfecting, oxidation.

Answer: C

CASE BASED MCQs

I. There are many substances which are used to detect the solutions as acidic or basic. They are called Acid-Base indicators. Depending upon the property of the indicator, we have different groups of Acid-Base indicators. Some indicators show different colours in acidic or basic medium and some indicators give different odours in acidic and basic medium. These indicators are either extracted from the plants or synthesised in the laboratory or industry.

Question. Which one of the following can be used as an acid-base indicator by visually impaired student?
A. Turmeric
B. Hibiscus
C. Vanilla
D. Litmus

Answer: C

Question. Select the incorrect option.
Indicator Colour in acidic medium Colour in basic medium
A. Litmus (Purple) Red Blue
B. Phenolphthalein (Colourless) Pink Colourless
C. Red cabbage extract (Purple) Red Green
D. Methyl orange (Orange) Red Yellow

Answer: B

Question. Which of the following will turn red litmus blue?
A. Amla juice
B. lemon juice
C. Soft drink
D. Baking soda

Answer: D

Question. A solution turns blue litmus red, the pH of the solution is likely to be-
A. 6
B. 7
C. 8
D. 9

Answer: A

II. Tajmahal, the seventh wonder of the world, is made of white stone. This white stone contains the same substance ‘A’ that is present in chalk powder and lime-stone. It is turning yellow due to polluted air. If it is cleaned by an acidic cleaner, a gas ‘B’ is released, which when passed through a solution ‘C’, forms the same substance which is present in the white stone that was used to make Tajmahal.

Question. Solution C is-
A. CaCl₂
B. CaCO₃
C. Ca(OH)₂
D. CaSO₄

Answer: C

Question. What is the nature of the substance A?
A. Acidic
B. Basic
C. Neutral
D. None

Answer: B

Question. The substance A is-
A. Ca₃CO₂
B. CaCO₃
C. Ca(OH)₂
D. CaSO₄

Answer: B

Question. Gas B is-
A. Hydrogen
B. Nitrogen
C. Chlorine
D. Carbon di oxide

Answer: D

III. A scale for measuring hydrogen ion concentration in a solution, called pH scale has been developed. The p in pH stands for ‘potenz’ in German, meaning power. On the pH scale we can measure pH from 0 to 14. pH should be thought of simply as a number which indicates the acidic or basic nature of a solution. Higher the hydronium ion concentration, lower is the pH value.

Question. A basic solution could have a pH of-
A. 3
B. 5
C. 7
D. 9

Answer: D

Question. The table provides the pH of four solutions P, Q, R and S.
Solution pH value
P 2
Q 9
R 5
S 11
Which of the following correctly represents the solutions in increasing order of their hydronium ion concentration?
A. P > Q > R > S
B. P > S > Q > R
C. S < Q < R < P
D. S < P < Q < R

Answer: C

Question. Which one of the following will have the highest hydrogen ion concentration?
A. pH = 1.1
B. pH = 2.2
C. pH = 3.3
D. pH = 4.4

Answer: A

Question. How is the hydrogen ion concentration and pH related to each other?
A. They are inversely proportional.
B. They are directly proportional.
C. They are equal.
D. They have no relation.

Answer: A

Acids Bases And Salts

ORAL QUESTIONS – (Conversation Type)

 

 

INTRODUCTION

The earliest classification of inorganic compounds including the large number of organic compounds was based on their taste. On this basis of these compounds were classified into acid, bases and salt. We use many such compounds in our daily lives, which are acids, bases and salt. We use curd, pickle, amla, soap and detergents, tamarind, toothpaste etc. We must learn to classify them based on scientific tests.

Test to distinguish between acids and bases
There are many substances, which show one colour or odour in the acidic medium and a different colour or odour in the basic medium. Such substances are called acid base indicators.

A. Indicators showing different colours in acidic and basic medium

a. Litmus solution as indicator is a purple coloured dye extracted from the lichen plant. It is the most commonly used indicator in the science laboratory. In the neutral solution, it has purple colour. In the acidic solution, it turns red whereas in the basic solution it turns blue. There are two types of litmus solution Blue and Red litmus solution. Red litmus solution is obtained by acidifying the purple litmus extract whereas blue litmus solution is obtained by making the purple litmus extract alkaline.

To test whether the given sample is acidic or basic, take few drops of distilled water in a test tube and two drops of blue litmus solution. Add few drops of sample substance that is to be tested. If the blue litmus solution changes into red colour, the substance is acidic. For instance, lemon juice, vinegar, orange juice, juice of unripe mangoes, tamarind all turn blue litmus solution to red. Thus, they are all acidic substances.

We may repeat the above experiment with red litmus solution. Those substances, which turn red litmus solution into blue colour, are bases. For instance, cucumber, washing soda solution, baking soda solution, bitter gourd etc. turn red litmus solution into blue. Thus, they are bases.

b. Synthetic indicators such as Phenolphthalein and Methyl orange

• Methyl orange is the compounds prepared industrially or in the laboratory. There are many such man-made substances, which can act as synthetic indicators.
• Phenolphthalein is colourless in neutral solution and in acidic solution but turns pink in basic solution.
• Methyl orange is of orange colour in neutral solution, red in acidic solution and yellow in basic solution.

Ask your teacher to help you classify various substance using these indicators.

B. Indicators giving different odours in acidic and basic medium. (Olfactory indicators)

• Clove oil
  Take two test tubes. Mark them test tube ‘A’ and test tube ‘B’. Add some hydrochloric acid in test tube ‘A’ and some Sodium Hydroxide in test tube ‘B’. Record the odour, of clove oil. Now add few drops of clove oil in each test tube and shake it gently. Smell the sample in test tube ‘A’ and ‘B’. Record the odour of each test tube. You will notice that the odour of acid and base after addition of clove oil is different. Ask your teacher to help you demonstrate the experiment in the laboratory.
• Vanilla essence.
  Repeat the experiment (a). Take another two test tubes and mark them ‘A’ and ‘B’. Add some acid ‘A’ and sodium hydroxide in ‘B’. Add some vanilla essence in each test tube (A) and (B). Vanilla retains its smell in acidic medium but looses its smell in basic medium.

C. Natural Indicators

Turmeric (Haldi), red cabbage, China rose peals are the natural indicators.

• Turmeric is yellow in colour. Turmeric leaves a yellow stain on clothes. When such stain is washed with detergents, the stain becomes brownish red. Detergents have the base called sodium hydroxide. This shows that the turmeric changes a base into brownish red colour. When the clothe is washed with lemon, it regains its yellow colour. This shows that brownish red colour of turmeric changes to yellow by acids.
• China rose petals act as a natural indicator. China rose indicator turns magenta (dark pink) in acidic solutions. It turns green in basic solutions and does not show any colour change in neutral solution.

Indicator Table

Indicator	Colour in the natural solution	Acids	Bases
Methyl orange	Orange	Red	Yellow
Phenolphthalein	Colourless	Colourless	Pink
Litmus	Purple	Red	Blue
Red Cabbage leaf	Red	Red	Green
Hydrangea Flower	Blue	Blue	Pink
Turmeric (Haldi)	Yellow	Yellow	Brownish red
China rose	No change in colour	Magenta	Green (Dark Pink)

ACID

An acid (from the Latin acidus meaning sour) is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion activity greater than in pure water. Chemicals or substances having the property of an acid are said to be acidic. Acids are sour in taste. Acids are of organic and inorganic nature. Acids found in plants and animals are organic in nature. Organic acids are weak whether inorganic acids are strong.

Organic Acids

Sl. No.	Source	Organic Acid
1.	Vinegar	Acetic Acid
2.	Apples	Malic Acid
3.	Tomatoes	Oxalic Acid
4.	Curd	Lactic Acid
5.	Proteins	Amino Acids
6.	Tamarind	Tartaric Acid
7.	Orange and lemon	Citric Acid
8.	Tea	Tannic Acid
9.	Ant and bee sting	Formic Acid
10.	Spinach	Oxalic Acid
11.	Sour Milk	Lactic Acid
12.	Sweat or urine	Uric Acid
13.	Vitamin C	Ascorbic Acid
14.	Grapes	Tartaric Acid

INORGANIC ACIDS are called mineral acids. They are prepared by dissolving mineral oxides in water. Sulphur dioxide dissolves in water to form sulphurous or sulphuric acid. Carbon dioxide dissolves in water to form carbonic acid. Hydrogen chloride dissolves in water to form hydrochloric acid etc.
a. Hydrochloric Acid
b. Nitric Acid
c. Phosphoric Acid
d. Sulphuric Acid.

PROPERTIES OF ACIDS

• Acids are generally sour in taste. (For example, the sour taste of lemon juice is due to citric acid.)
• Strong or concentrated acids or their fumes often produce a stinging feeling on mucous membranes.
• Change the colour of pH indicators as follows: turn blue litmus and methyl orange red, turn phenolphthalein colourless.
• React with metals to produce a metal salt and hydrogen.
• React with metal carbonates to produce water, \( CO_2 \) and a salt.
• React with metal hydroxides and metal oxides to produce water and a salt.
• Conduct electricity, depending on the degree of dissociation in aqueous solution. Car batteries use acids in them.
• Acids can be gases, liquids, or solids. Respective examples (at 20ºC and one atm) are hydrogen chloride, sulphuric acid and citric acid. Solutions of acids in water are liquids, such as hydrochloric acid-an aqueous solution of hydrogen chloride. At 20ºC and one atm, linear carboxylic acids are liquids and solids beginning from decanoic acid (ten carbon atoms). Perfumed carboxylic acids, the simplest being benzoic acid, are solids.
• Strong acids and some concentrated weak acids are corrosive and can cause severe burns even after short contact.

BASES

Strong bases, like strong acids, attack living tissue and cause serious burns. They react differently to skin than acids do, so while strong acids are corrosive, we say that strong bases are caustic (corrosive). Bases may also be weak bases such as ammonia, which is used for cleaning. Arrhenius bases are water soluble. An alkali is a special example of a base, where in an aqueous environment; hydroxide ions (also viewed as \( OH^- \)) are donated. Bases, which dissolve in water, are called alkalis. Bases are alkalis but not all alkalis are bases.

The notion of a base as a concept in chemistry was first introduced by the French chemist Guillaume Francois Rouelle in 1754. He noted that acids, which in those days were mostly volatile liquids (like acetic acid), turned into solid salts only when combined with specific substances. These substances form a concrete base for the salt and hence the name.

PROPERTIES OF BASES

• Slippery or soapy feel on fingers, due to specification of the lipids in human skin
• Concentrated or strong bases are caustic (corrosive) on organic matter and react violently with acidic substances
• Aqueous solutions (bases dissolved in water) or molten bases dissociate in ions and conduct electricity
• Reactions with indicators: bases turn litmus paper blue and phenolphthalein pink

In chemistry, a base is most commonly thought of as an aqueous substance that can accept hydrogen ions. A base is also often referred to as an alkali if \( OH^- \) ions (hydroxide ions) are involved. Examples of simple bases are sodium hydroxide and ammonia. Although ammonia does not directly contain an \( OH^- \) group in its, formula, it produces one in water i.e. Ammonium hydroxide. All compound containing hydroxide are bases. For example, Sodium hydroxide (NaOH), Potassium hydroxide (KOH), Magnesium hydroxide [\( Mg(OH)_2 \)], Calcium hydroxide [\( Ca(OH)_2 \)] etc.

Bases can be thought of as the chemical opposite of acids. A reaction between an acid and base is called neutralization. Bases and acids are seen as opposites because the effect on an acid is to increase the hydronium ion (\( H_3O^+ \)) concentration in water, whereas bases reduce this concentration. Bases react with acids to produce water and salts (or their solutions). Acids react with bases to form salt and water.

• Hydrochloric acid reacts with sodium hydroxide to form common salt called sodium chloride and water. This reaction supports neutralization.
• Farmers use slaked lime [calcium hydroxide, \( Ca(OH)_2 \)] or quick lime [calcium oxide, \( CaO \)] to neutralise the acidic effects of soil in their farms.
• In case the soil is basic, organic matter is used to release or neutralise the bases.
• Bacterias are continuously produced in our mouth, which causes tooth decay by making acids. Basic nature of toothpaste and toothpowder prevents tooth decay by neutralizing the acidic effects.
• A small amount of hydrochloric acid available in our stomach helps digesting food and kills the germs. Its excess production in stomach causes indigestion. To neutralize the effects of acid magnesium hydroxide (milk of magnesia) tablets are used.
• Baking Soda [Sodium bicarbonate, \( NaHCO_3 \)] is used to treat bee sting or ant sting. Their sting release formic acid on the skin is neutralized by bases.

SALT

A salt, in chemistry, is defined as the product formed from the neutralization reaction of acids and bases. There are several varieties of salts. Salts that produce hydroxide ions when dissolved in water are basic salts and salts that produce hydronium ions in water are acid salts. Neutral salts are those that are neither acid nor basic salts.

When salts are dissolved in water, they are called electrolytes, and are able to conduct electricity, a property that is shared with molten salts. Sodium Chloride (NaCl), Magnesium Chloride (\( MgCl_2 \)), Calcium Carbonate (\( CaCO_3 \)), Calcium Sulphate (\( CaSO_4 \)) etc. are some examples of salt. Not all salt are edible. Salts can be poisonous to the body as well. Not all salts are salty. Salt that we add to our food is Sodium Chloride (NaCl).

EXERCISE - I (COMPETITIVE CORNER)

(A) Choose the correct option.

Question. 1. Acids are formed when
(a) metals combine with oxygen
(b) oxides of nonmetals dissolve in water
(c) metals react with water
(d) bases dissolve in water
Answer: C

Question. 2. Hydrochloric acid can be neutralised by
(a) nitric acid
(b) sulphuric acid
(c) citric acid
(d) sodium hydroxide
Answer: D

Question. 3. A soap solution is
(a) acidic
(b) alkaline
(c) neutral
(d) None
Answer: B

Question. 4. In a neutralisation reaction, an acid reacts with a base to give
(a) another acid
(b) another base
(c) another acid and another base
(d) a salt and water
Answer: D

(B) Match the columns A and B

Question. 1. Match the columns A and B
(a) Hydrochloride acid
(b) Ascorbic acid
(c) Sulphuric acid
(d) Lactic acid
(e) Acetic acid

(i) In storage batteries
(ii) Found in yoghurt
(iii) In making vinegar
(iv) As bathroom acid
(v) Vitamin C
Answer: (a) – (iv), (b) – (v), (c) – (i), (d) – (ii), (e) – (iii)

Question. 2. Match the columns A and B
(a) Sodium iodate
(b) Calcium sulphate
(c) Bleaching powder
(d) Ammonium sulphate
(e) Sodium benzoate

(i) A food preservative
(ii) Used as a fertiliser
(iii) Present in plaster of Paris
(iv) A disinfectant
(v) A supplement to common salt
Answer: (a) – (v), (b) – (iii), (c) – (iv), (d) – (ii), (e) – (i)

(C) Tick the correct box.

Question. 1. Are most salts neutral ?
Answer: No

Question. 2. Are soluble bases called alkalis ?
Answer: Yes

Question. 3. Calcium carbonate when heated gives calcium oxide, which is a base. Will the same base be formed when calcium chloride is heated ?
Answer: No

Question. 4. Lemon juice gives carbon dioxide with baking soda. Will it give carbon dioxide with marble too ?
Answer: Yes

Question. 5. Carbon when burnt in air gives an acidic gas. Does sulphur when burnt in air give and an acidic gas ?
Answer: Yes

EXERCISE - II (CBSE CORNER)

(A) Answer the following in not more than 20 words.

Question. 1. Classify the following substances into acidic and basic substances. Tomato juice, soap solution, toothpaste, lemon juice, vinegar
Answer: Acidic: Tomato juice, lemon juice, vinegar. Basic: Soap solution, toothpaste.

Question. 2. Name three mineral acids and give their formulae.
Answer: 1. Hydrochloric acid (HCl), 2. Nitric acid (\( HNO_3 \)), 3. Sulphuric acid (\( H_2SO_4 \)).

Question. 3. Define acids
Answer: Acids are sour chemical compounds that, when dissolved in water, increase the hydrogen ion activity.

Question. 4. Define bases
Answer: Bases are chemical compounds that feel slippery, have a bitter taste, and turn red litmus paper blue.

Question. 5. What are soluble bases called ? Give two examples.
Answer: Soluble bases are called alkalis. Examples include Sodium hydroxide and Potassium hydroxide.

Question. 6. Define neutral substances and indicators.
Answer: Neutral substances are neither acidic nor basic. Indicators are substances that show different colours or odours in acidic and basic media.

(B) Answer the following in not more than 40 words.

Question. 1. Name an acidic gas which is discharged into the atmosphere on the burning of fuels like coal and natural gas. How is this gas formed ?
Answer: Carbon dioxide or sulphur dioxide. These gases are formed when the carbon or sulphur in the fuels reacts with oxygen in the air during combustion.

Question. 2. What are the general properties of basic substances ?
Answer: Basic substances are bitter in taste, feel slippery or soapy, turn red litmus paper blue, and react with acids to form salt and water.

(C) Answer the following in not more than 100 words.

Question. 1. Write the properties of an acid
Answer: Acids are sour in taste, turn blue litmus and methyl orange red, react with metals to produce salt and hydrogen, and react with carbonates to produce \( CO_2 \).

Question. 2. Describe an activity to show the effect of an acid on carbonates and hydrogencarbonates
Answer: Adding an acid like HCl to sodium carbonate results in the production of carbon dioxide gas, which can be identified by passing it through lime water, turning it milky.

Question. 3. What is acid rain ? How is it formed ? Mention three bad effects of acid rain.
Answer: Acid rain is rain containing high levels of nitric and sulphuric acids. It is formed when pollutants like \( SO_2 \) and \( NO_2 \) react with atmospheric moisture. It corrodes buildings, harms aquatic life, and damages forests.

Question. 4. Write a note on the uses of bases.
Answer: Bases are used in manufacturing soap (Sodium hydroxide), treating soil acidity (Calcium hydroxide), and as antacids (Magnesium hydroxide) to relieve indigestion.

Question. 5. Why factory waste is neutralised before disposing it into the water bodies?
Answer: Factory wastes often contain high concentrations of acids which can kill fish and other aquatic organisms. Neutralisation makes the waste less harmful to the environment.

(D) Complete the following.

Question. 1. The sour things we eat contain…..
Answer: acids

Question. 2. Ammonium hydroxide is an…..
Answer: alkali

Question. 3. An acid is……by a base
Answer: neutralized

Question. 4. An antacid generally contains……
Answer: a base

Question. 5. Acid + base ___ + ___
Answer: Salt + Water

Question. 6. Complete the table:
Indicator - Acidic medium Colour - Basic medium Colour
Litmus - Red - Blue
Phenolphthalein - Colourless - Pink
Turmeric juice - Yellow - Red-brown
Red-cabbage juice - Red - Green
China-rose juice - Red - Magenta/Green
Answer: (As per table on page 107)