CBSE Class 10 Science Acids Bases And Salts Worksheet Set C

Question. Which of the following gives the correct increasing order of acidic strength?
(a) Water< Acetic acid <Hydrochloric acid
(b) Water<Hydrochloric acid <Acetic
(c) Acetic acid < Water < Hydrochloric acid
(d) Hydrochloric acid < water < Acetic acid

Answer: A

Question. The pH of gastric juices released during digestion is:
(a) less than 7
(b) more than 7
(c) equal to 7
(d) equal to 0 

Answer: A

Question. Which one of the following types of medicines is used for treating indigestion?
(a) Antibiotic
(b) Analgesic
(c) Antacid
(d) Antiseptic 

Answer: C

Question. The acid having highest hydrogen ion concentration is one with
(a) pH=2.5
(b)pH = 1.8
(c) pH=7
(d) pH=10 

Answer: B

Question. 10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a given solution of HCl. If we take 20 mL of the same solution of NaOH, the amount of HCl solution (the same solution as before) required to neutralise it will be
(a) 4 mL
(b) 8mL
(c) 12 mL
(d) 16 mL

Answer: D

Question. A solution reacts with crushed egg-shells to give a gas that turns lime-water milky. The solution contains
(a) NaCl
(b) HCl
(c) LiCl
(d) KCl

Answer: B

Question. Which of the following salts does not contain water of crystallisation?
(a) Blue vitriol
(b) Baking soda
(c) Gypsum
(d) Washing soda 

Answer: B

Question. A solution turns red litmus blue, its pH is likely to be
(a) 1
(b) 4
(c) 5
(d) 10 

Answer: D

Question. Common salt, besides used in kitchen, can also be used as the raw material for making:
(i) Washing soda
(ii) Baking soda
(iii) bleaching powder
(iv) slaked lime
(a) (i) and (ii)
(b) (i) and (iii)
(c) (i), ii) and (iii)
(d) (i),(iii) and (iv)

Answer: C

Question. Assertion (A) - The aqueous solutions of glucose and alcohol do not show acidic character.
Reason (R) – Aqueous solutions of glucose and alcohol do not give H⁺ ions.
(a) Both A and R are true and R is correct explanation of A
(b) Both A and R are true and R is not correct explanation of A
(c) A is true but R is false
(d) A is false but R is true

Answer: A

Question. Assertion (A) - Carbonic acid is weak acid.
Reason (R) – It ionized completely in aqueous solution.
(a) Both A and R are true and R is correct explanation of A
(b) Both A and R are true and R is not correct explanation of A
(c) A is true but R is false
(d) A is false but R is true

Answer: C

Question. Write the chemical name and formula of the compound which is used as an antacid.
Answer: Sodium bicarbonate, NaHCO₃

Question. Why does an aqueous solution of an acid conduct electricity? 
Answer. Acids dissociate in aqueous solutions to form ions. These ions are responsible for conduction of electricity.

Question. What is baking powder? How does it make the cake soft and spongy?
Answer:  Baking powder is a mixture of sodium hydrogen carbonate and tartaric acid. On heating it
liberates CO₂ which makes the cake soft and spongy

Question. Write the chemical name of Plaster of Paris. Write a chemical equation to show the reaction between Plaster of Paris andwater. Name the compound produced in this reaction.
Answer:  Calcium Sulphate hemihydrate.
CaSO₄.½ H₂O +1½ H₂O CaSO₄.2H₂O
The compound produced is Gypsum.

Question. Why does dry HCl gas not change the colour of the dry litmus paper?
Answer. Colour of the litmus paper is changed by the hydrogen ions. Dry HCl gas does not contain H⁺ ions. It is only in the aqueous solution that an acid dissociates to give ions.
Since in this case, neither HCl is in the aqueous form nor the litmus paper is wet, therefore, the colour of the litmus paper does not change.

Question. What is the common name of the compound CaOCl₂?
Answer. The common name of the compound CaOCl₂ is bleaching powder.

Question. Write the name of the products formed by heating gypsum at 373K.Write one use of it.
Answer:  Plaster of Paris and water. It is used for plastering fractured bone.

Question. Under what soil condition do you think a farmer would treat the soil of his fields with quick lime (calcium oxide) or slaked lime (calcium hydroxide) or chalk calcium carbonate)?
Answer. If the soil is acidic and improper for cultivation, then to increase the basicity of soil, the farmer would treat the soil with quick lime or slaked lime or chalk.

Question. A gas X reacts with lime water and forms a compound Y which is used as bleaching agent in the chemical industry. Identify X and Y .Give the chemical equation of the reaction involved.
Answer:  X is chlorine Y is CaOCl2 (calcium oxy chloride) used as bleaching agent.
Ca (OH) ₂+ Cl₂ -----> CaOCl₂ +H₂O

Question. While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?
Answer. Since the process of dissolving an acid in water is exothermic, it is always recommended that acid should be added to water. If it is done the other way, then it is possible that because of the large amount of heat generated, the mixture splashes out and causes burns. 

Question. What effect does the concentration of H⁺_(aq) ions have on the nature of the solution?
Answer. Concentration of H⁺_(aq) can have a varied effect on the nature of the solution. With an increase in H⁺ ion concentration, the solution becomes more acidic, while a decrease of H⁺ ion causes an increase in the basicity of the solution.

Question. Do basic solutions also have H⁺_(aq) ions? If yes, then why are these basic?
Answer. Yes, basic solution also has H⁺_(aq) ions. However, their concentration is less as compared to the concentration of OH⁻ ions that makes the solution basic.

Question. You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?
Answer. If the colour of red litmus paper gets changed to blue, then it is a base and if there is no colour change, then it is either acidic or neutral. Thus, basic solution can be easily identified.
Let us mark the three test tubes as A, B, and C. A drop of the solution in A is put on the red litmus paper. Same is repeated with solution B and C. If either of them changes colour to blue, then it is basic.Therefore, out of three, one is eliminated. Out of the remaining two, any one can be acidic or neutral. Now a drop of basic solution is mixed with a drop of each of the remaining two solutions separately and then the nature of the drops of the mixtures is checked. If the colour of red litmus turns blue, then the second solution is neutral and if there is no change in colour, then the second solution is acidic. This is because acidic and basic solutions neutralize each other. Hence, we can distinguish between the three types of solutions.

Question. Why should curd and sour substances not be kept in brass and copper vessels?
Answer. Curd and other sour substances contain acids. Therefore, when they are kept in brass and copper vessels, the metal reacts with the acid to liberate hydrogen gas and harmful products, thereby spoiling the food.

Question. Name the substance which on treatment with chlorine yields bleaching powder?
Answer. Calcium hydroxide [Ca (OH)₂], on treatment with chlorine, yields bleaching powder.

Question. Name the sodium compound which is used for softening hard water.
Answer. Washing soda (Na₂CO₃.10H₂O) is used for softening hard water.

Question. (a) Crystals of a substance changed their color on heating in a closed test tube but regained it after some time when they were allowed to cool down. Name the substance and write its formula .Explain the phenomenon.
(b) How is sodium carbonate prepared? Give two uses of the compound
Answer:  (a) Copper sulphate, CuSO₄.5H₂O.
It is blue. It becomes white on heating due to loss of water molecule.
_Heat 
CuSO₄.5H₂O → CuSO₄+5 H₂O
It regains its colour by absorbing water from atmosphere
_Heat 
CuSO₄+5H₂O → CuSO₄.5 H₂O
(b) Prepared by passing CO₂ through ammoniacal brine Used for production of washing powder& manufacture of glass

Question. Given below are the pH values of different liquids.7.0, 14.0, 4.0, and 2.0.Which of these could be that of
(a) lemon juice
(b) distilled water
(c) sodium hydroxide solution
(d) tomato juice.
Answer:  (a) lemon juice- 2.0
(b) distilled water-7.0
(c) sodium hydroxide solution `14.0
(d) tomato juice- 4.0

Question. Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A, while acetic acid (CH₃COOH) is added to test tube B. In which test tube will the fizzing occur more vigorously and why?
Answer. The fizzing will occur strongly in test tube A, in which hydrochloric acid (HCl) is added.
This is because HCl is a stronger acid than CH₃COOH and therefore produces hydrogen gas at a faster speed due to which fizzing occurs.

Question. Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain your answer.
Answer. The pH of milk is 6. As it changes to curd, the pH will reduce because curd is acidic in nature. The acids present in it decrease the pH.

Question. Why do acids not show acidic behaviour in the absence of water?
Answer. Acids do not show acidic behaviour in the absence of water because the dissociation of hydrogen ions from an acid occurs in the presence of water only. It is the hydrogen ions that are responsible for the acidic behaviour.

Question. Give two important uses of washing soda and baking soda.
Answer. Two important used of washing soda and baking soda are as follows:
(1) Washing soda:
(a) It is used in glass, soap, and paper industries.
(b) It is used to remove permanent hardness of water.
(2) Baking soda:
(a) It is used as baking powder. Baking powder is a mixture of baking soda and a mild acid known as tartaric acid. When it is heated or mixed in water, it releases CO₂ that makes bread or cake fluffy.
(b) It is used in soda-acid fire extinguishers.

Question.How is the concentration of hydronium ions (H₃O⁺) affected when a solution of an acid is diluted?
Answer. When an acid is diluted, the concentration of hydronium ions (H₃O⁺) per unit volume decreases. This means that the strength of the acid decreases.

Question. You have two solutions, A and B. The pH of solution A is 6 and pH of solution B is 8. Which solution has more hydrogen ion concentration? Which of this is acidic and which one is basic?
Answer. A pH value of less than 7 indicates an acidic solution, while greater than 7 indicates a basic solution. Therefore, the solution with pH = 6 is acidic and has more hydrogen ion concentration than the solution of pH = 8 which is basic. 

Question. Why does distilled water not conduct electricity, whereas rain water does?
Answer. Distilled water is a pure form of water and is devoid of any ionic species. Therefore, it does not conduct electricity. Rain water, being an impure form of water, contains many ionic species such as acids and therefore it conducts electricity.

Question. How is the concentration of hydroxide ions (OH⁻) affected when excess base is dissolved in a solution of sodium hydroxide?
Answer. The concentration of hydroxide ions (OH⁻) would increase when excess base is dissolved in a solution of sodium hydroxide.

Question. A milkman adds a very small amount of baking soda to fresh milk.
(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline?
(b) Why does this milk take a long time to set as curd?
Answer. (a) The milkman shifts the pH of the fresh milk from 6 to slightly alkaline because in alkaline condition, milk does not set as curd easily.
(b) Since this milk is slightly basic than usual milk, acids produced to set the curd are neutralized by the base. Therefore, it takes a longer time for the curd to set.

Question. (a) A milk man adds a very small amount of baking soda to fresh milk.Why does he shift the pH of the fresh milk from 6 to slightly alkaline?
(b)Mention pH range within which our bodyworks?
(c) Explain how antacids give relief from acidity.
(d) Mention the nature of tooth pastes .How do they prevent tooth decay?
Answer:  (a) It is done to prevent the formation of lactic acid which spoils the milk
(b) pH range 7.0- 7.8
(c) Antacids neutralizes excess of acid in our body and gives relief.
(d) Basic. Neutralize the acid formed in the mouth

Question. Five solutions A, B, C, D and E when tested with universal indicator showed pH as 4, 1,
11, 7 and 9, respectively. Which solution is
(a) neutral?
(b) strongly alkaline?
(c) strongly acidic?
(d) weakly acidic?
(e) weakly alkaline?
Arrange the pH in increasing order of hydrogen-ion concentration.
Answer. (a) Neutral → Solution D with pH 7
(b) Strongly alkaline → Solution C with pH 11
(c) Strongly acidic → Solution B with pH 1
(d) Weakly acidic → Solution A with pH 4
(e) Weakly alkaline → Solution E with pH 9
The pH can be arranged in the increasing order of the concentration of hydrogen ions as:
11 < 9 < 7 < 4 < 1