CBSE Class 10 Science Acids Bases And Salts Worksheet Set A

MCQ Questions for NCERT Class 10 Science Acids Bases And Salts

iii. Hydrolysis of a salt of a weak acid and a weak base. They give acidic, neutral or basic (or alkaline) solutions in water depending upon the nature of weak acid and a weak base from which salt is produced.

e.g. Ammonium acetate (CH₃COONH₄) gives neutral solution on hydrolysis.

Ammonium carbonate, (NH₄)CO₃ given neutral solution on hydrolysis. 

e.g. NaCl, KCl, KNO₃ NaNO₃ etc.

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 does not change then it is acid. If the colour of red litmus changes to blue then it is base. If there is slight change in the colour of red litmus (such as purple) then it is distilled water.

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. Which gas is usually liberated when an acid reacts with a metal? Illustrate with an example. How will you test for the presence of this gas?
Answer Hydrogen gas is usually liberated when an acid reacts with a metal.Take few pieces of zinc granules and add 5 ml of dilute H₂SO₄. Shake it and pass the
gas produced into a soap solution. The bubbles of the soap solution are formed. These soap bubbles contain hydrogen gas.
H₂SO₄ + Zn → ZnSO₄ + H₂ ↑
We can test the evolved hydrogen gas by its burning with a pop sound when a candle is brought near the soap bubbles.

Question. Metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.
Answer CaCO₃ (s) + 2HCl (aq) → CaCl₂ (aq) + CO₂ (g) + H₂O (l)
Calcium Carbonate + Hydrochloric acid → Calcium Chloride + Carbon dioxide + Water

Question. Why do HCl, HNO₃, etc., show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character?
Answer When HCl or HNO₃ are mixed with water then they dissolve in water to form H+ or
H₃O⁺ ions which shows their acidic character. For example just see the following reactions
HCl (aq) → H⁺ + Cl^-
H⁺ + H₂O → H₃O⁺
When alcohols and glucose are mixed with water then they do not dissolve to form ions.
Hence they do not show acidic character.

Question. Why does an aqueous solution of an acid conduct electricity?
Answer : The presence of hydrogen (H+) or hydronium (H3O+) ions in the aqueous solution of an acid are responsible for conducting electricity.

Question. Why does dry HCl gas not change the colour of the dry litmus paper?
Answer : Dry HCl gas not change the colour of the dry litmus paper because it has no Hydrogen ions (H+) in it.

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. 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. 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. 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. What effect does the concentration of H+ (aq) ions have on the nature of the solution?
Answer : If the concentration of H+ (aq) ions is increased (>10-7) then the solution become acidic and if the concentration of H+ (aq) ions is decreased (<10-7) then the solution become basic in nature.

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

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. What is the common name of the compound CaOCl₂?
Answer : Bleaching Powder.

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

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

Question. What will happen if a solution of sodium hydrocarbonate is heated? Give the equation of the reaction involved.
Answer :  When sodium hydrogen carbonate is heated then sodium carbonate and water is formed along with the evolution of carbon dioxide gas. 

Excercise

Question. A solution turns red litmus blue, its pH is likely to be
(a) 1
(b) 4
(c) 5
(d) 10
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. 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. Which one of the following types of medicines is used for treating indigestion?
(a) Antibiotic
(b) Analgesic
(c) Antacid
(d) Antiseptic
Answer : C

Question. Write word equations and then balanced equations for the reaction taking place when−
(a) dilute sulphuric acid reacts with zinc granules.
(b) dilute hydrochloric acid reacts with magnesium ribbon.
(c) dilute sulphuric acid reacts with aluminium powder.
(d) dilute hydrochloric acid reacts with iron filings.
Answer :
(a) H₂SO₄ (aq) + Zn (s) → ZnSO₄ (aq) + H₂ (g)
(b) 2HCl (aq) + Mg (s) → MgCl (aq) + H₂ (g)
(c) 3H₂SO₄ (aq) + 2Al (s) → Al₂SO₄ (aq) + 3H₂ (g)
(d) 6HCl (aq) + 2Fe (s) → 2FeCl₃ (aq) + 3H₂ (g)

Question. Compounds such as alcohols and glucose also contain hydrogen but are not categorized as acids. Describe an activity to prove it.
Answer : Two nails are fitted on a cork and are kept it in a 100 mL beaker. The nails are then connected to the two terminals of a 6-volt battery through a bulb and a switch. Some dilute HCl is poured in the beaker and the current is switched on. The same experiment is then performed with glucose solution and alcohol solution.
Observations: It will be observed that the bulb glows in the HCl solution and does not glow in the glucose solution.
Result: HCl dissociates into H+and Cl−ions. These ions conduct electricity in the solution resulting in the glowing of the bulb. On the other hand, the glucose solution does not dissociate into ions. Therefore, it does not conduct electricity.
Conclusion: From this activity, it can be concluded that all acids contain hydrogen but not all compounds containing hydrogen are acids.
That is why, though alcohols and glucose contain hydrogen, they are not categorised as acids.

Question. Why does distilled water not conduct electricity, whereas rain water does?
Answer : Distilled water cannot conduct electricity because it does not contain ions while rain water conducts electricity as it contains ions due presence of dissolved salts in it.

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.

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.

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. 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. Plaster of Paris should be stored in a moisture-proof container. Explain why?
Answer : The Plaster of Paris should be stored in a moisture-proof container as it absorbs water from moisture and turn into hard substance (Gypsum) as shown in following chemical equation.

Question. What is a neutralization reaction? Give two examples.
Answer : A reaction in which an acid and base react with each other to give a salt and water is termed as neutralization reaction.For Example:
(i) NaOH + HCl → NaCl + H₂O
(ii) HNO₃ + KOH → KNO₃ + H₂O

Question. Give two important uses of washing soda and baking soda.
Answer : Two important uses of washing soda are:
→ It is used in glass, soap, and paper industries.
→ It is used to remove permanent hardness of water.
Two important uses of baking soda are:
→ 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.
→ It is used in soda-acid fire extinguishers.

Question. An aqueous solution ‘A’ turns phenol-phthalein solution pink. On addition of an aqueous solution ‘B’ to ‘A’ and ‘B’.
(a) A is strongly basic and B is a weak base.
(b) A is strongly acidic and B is a weak acid.
(c) A has pH greater than 7 and B has pH less than 7.
(d) A has pH less than 7 and B has pH greater than 7.
Answer : D

Question. When you add a few drops of acetic acid to a test-tube containing sodium bicarbonate powder, which one of the following is your observation ?
(a) No reaction takes place.
(b) A colourless gas with pungent smell is released with brisk effervescence.
(c) A brown coloured gas is released with brisk effervescence.
(d) Formation of bubbles of a colourless and odourless gas.
Answer : D

Question. A student requires hard water for an experiment in his laboratory which is not available in the neighbouring area. In the laboratory there are some salts, which when dissolved in distilled water can convert it into hard water. Select from the following groups of salts, a group, each salt of which when dissolved in distilled water will make it hard.
(a) Sodium chloride, potassium chloride
(b) Sodium sulphate, potassium sulphate
(c) Sodium sulphate, calcium sulphate
(d) Calcium sulphate, calcium chloride
Answer : D

Question. You have four test tubes, A, B, C and D containing sodium carbonate, sodium chloride, lime water and blue litmus solutions respectively. Out of these the material of which test tube/test tubes would be suitable for the correct test of acetic/ethanoic acid ?
(a) Only A
(b) A and B
(c) B and C
(d) A and D
Answer : D

Question. For demonstrating the preparation of soap in the laboratory which of the following combination of an oil and a base would be most suitable ?
(a) Mustard oil and calcium hydroxide
(b) Castor oil and calcium hydroxide
(c) Turpentine oil and sodium hydroxide
(d) Mustard oil and sodium hydroxide.
Answer : D

Question. A student took four test tubes P, Q, R and S and filled about 8 ml. of distilled water in each. After that he dissolved an equal amount of Na₂SO₄ in P, K₂SO₄ in Q, CaSO₄ in R and MgSO₄ in S. On adding an equal amount of soap solution and shaking each test tube well, a good amount of lather will be obtained in the test tubes :
(a) P and Q
(b) P and R
(c) P, Q and S
(d) Q, R and S
Answer : A

Question. If you take some distilled water in a test-tube, add an equal amount of acetic acid to it, shake the test-tube well and leave it undisturbed on the test-tube stand, then after about 5 minutes, what would you observe ?
(a) There is a layer of water over the layer of acetic acid.
(b) A precipitate is settling at the bottom of the testtube.
(c) Bubbles of colourless gas are coming out of the test-tube.
(d) There is a clear, colourless transparent solution in the test-tube.
Answer : D

Question. Which of the following is used for dissolution of gold ?
(a) Hydrochloric acid
(b) Sulphuric acid
(c) Nitric acid
(d) Aqua regia
Answer : D

Question. Which of the following is not a mineral acid ?
(a) Hydrochloric acid
(b) Citric acid
(c) Sulphuric acid
(d) Nitric acid
Answer : B

Question. Which among the following is not a base ?
(a) NaOH
(b) KOH
(c) NH₄OH
(d) C₂H₅OH
Answer : D

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

Question. Sodium hydrogen carbonate when added to acetic acid evolves a gas. Which of the following statements are true about the gas evolved ?
(i) It turns lime water milky.
(ii) It extinguishes a burning splinter.
(iii)It dissolves in a solution of sodium hydroxide.
(iv)It has a pungent odour.
(a) (i) and (ii)
(b) (i), (ii) and (iii)
(c) (ii), (iii) and (iv)
(d) (i) and (iv)
Answer : B

Question. If a few drops of a concentrated acid accidentally spills over the hand of a student, what should be done ?
(a) Wash the hand with saline solution.
(b) Wash the hand immediately with plenty of water and apply a paste of sodium hydrogen carbonate.
(c) After washing with plenty of water apply solution of sodium hydroxide on the hand.
(d) Neutralise the acid with a strong alkali.
Answer : B

Question. One of the constituents of baking powder is sodium hydrogen carbonate, the other constituent is :
(a) Hydrochloric acid
(b) Tartaric acid
(c) Acetic acid
(d) Sulphuric acid
Answer : B

Question. Which of the following phenomena occur, when a small amount of acid is added to water ?
(i) Ionisation,  (ii) Neutralisation,
(iii) Dilution,     (iv) Salt formation.
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iii)
(d) (ii) and (iv)
Answer : B

Question. Which one of the following can be used as an acid– base indicator by a visually impaired student?
(a) Litmus
(b) Turmeric
(c) Vanilla essence
(d) Petunia leaves
Answer : C

Question. Which of the following substance will not give carbon dioxide on treatment with dilute acid ?
(a) Marble
(b) Limestone
(c) Baking soda
(d) Lime
Answer : D

Question. Match the following
Column I                          Column II
(a) Bleaching powder        (i) Preparation of glass
(b) Baking soda               (ii) Production of H₂ and Cl₂
(c) Washing soda             (iii) Decolourisation
(d) Sodium chloride          (iv) Antacid
Answer : (a) (iii), (b) (iv), (c) (i), (d) (ii)

Question. Fill in the blanks

(a) The pH of the gastric juices released during digestion is .................. .
(b) When acid reacts with a metal, .................. gas is evolved.
(c) On heating gypsum, it loses water molecules and form .................. .
Answer :
(a) Less than 7, (b) H₂ (hydrogen), (c) CaSO₄. 1/2H₂O (Plaster of paris).

Assertion and Reasoning Based Questions
Directions : In the following questions, a statement of assertion is followed by a statement of reason. Mark the correct choice as :
(a) If both assertion and reason are true and reason is the correct explanation of assertion.
(b) If both assertion and reason are true, but reason is not the correct explanation of assertion.
(c) If assertion is true, but reason is false.
(d) If assertion is false but reason is true.

Question. Assertion : Solutions of compounds like alcohol and glucose do not show acidic character.
Reason : They do not show acidic character because they do not dissociate into ions.
Answer : A

Question. Assertion : Dry HCl gas does not change the colour of the dry litmus paper.
Reason : It is because dry HCl does not contain the OH– ions.
Answer : C

Question. Assertion : Curd and sour substances should not be stored in copper vessels.
Reason : Curd and other sour substances should not be kept in brass and copper vessels as they contain acids.
Answer : A

Question. Assertion : Calcium starts floating when added in water.
Reason : Calcium starts floating because the bubbles of oxygen gas which are formed during the reaction stick to the surface of the metal.
Answer : C

Question. Assertion : Tap water conducts electricity but distilled water does not conducts electricity.
Reason : Tap water contains ions whereas distilled water does not contain ions.
Answer : A

Question : Name the acid along with its'chemical formula present in ant sting.
Answer :  The acid present in ant sting is methanoic acid (formic acid). The chemical formula is HCOOH. Explanation: When an ant stings, it leaves formic acid (Methanoic acid) which causes pain and irritation. To get relief from the sting, mild base like baking soda on the stung area gives relief. 

Question : A solution ‘X’ gives orange colour when a drop of it falls on pH paper, while another solution ‘Y’ gives bluish colour when a drop of it falls on pH paper. What is the nature of both the solutions? Determine the pH of solutions ‘X’ and ‘Y’.
Answer :  Comparing with the pH chart, we find that orange colour corresponds to pH value of about 4 and blue colour to pH value of about 10. (1) X is therefore acidic and pH is around 4. (2) Y is basic having a pH of about 10. 

Question : The pH of soil A is 7.5 while that of soil B is 4.5. Which of the two soils should be treated with chalk and why?
Answer :  Chalk or CaCO₃ is basic in nature. As the soil B having pH 4.5 is acidic, it should be treated with powdered chalk to reduce its acidity by increasing its pH. Soil A is slightly alkaline. 

Question : Blue litmus solution is added to two test tubes A and B containing dilute HCl and NaOH solution respectively. In which test tube a colour change will observed? State the colour change and give its reason.
Answer : Colour change will be observed in Test tube A containing dil HCl. It will change the colour of blue litmus to red. Test tube contains dil HCl which is an acid and acids turn the colour of blue litmus to red as they contain H+ ions. 

Question : What types of ions are formed:
(a) when an acid is dissolved in water
(b) when a base is dissolved in water ?
Answer :  When an acid is dissolved in water, it forms hydrogen or H+ ions whereas it forms hydroxide or OH- ions when a base is dissolved in water.

Question : State the effect of concentration of H⁺(aq) ions on the nature of the solution. Do basic solutions also have H⁺(aq) ions ? If yes, then why are these basic? 
Answer :  The solution becomes more acidic when the concentration of H+ (aq) ions increases. Yes, basic solutions also have H+ (aq) ions. They are basic as the concentration of OH– ions is more than that of H+ ions in the solution.