Acids, Bases and Salts (Question Bank)

📝 Acids, Bases, and Salts

Multiple Choice Questions

1) Our body works within the pH range of

(a) 5.6 to 7.0

(b) 7.0 to 7.8

(d) 3.5 to 6.0

Ans: (b)

2) A sample of soil is mixed with water and allowed to settle. The clear supernatant solution turns the pH paper yellowish-orange. Which of the following would change the colour of this pH paper to greenish-blue?

(a) Lemon juice

(b) Vinegar

(d) An antacid

Ans: (d)

3) Which of the following statements is correct about an aqueous solution of an acid and of a base?

(i) Higher the pH, stronger the acid

(ii) Higher the pH, weaker the acid

(iii) Lower the pH, stronger the base

(iv) Lower the pH, weaker the base

(a) (i) and (iii)

(b) (ii) and (iii)

(d) (ii) and (iv)

Ans: (d)

4) The pH of the gastric juices released during digestion is

(a) less than 7

(b) more than 7

(d) equal to 0

Ans: (a)

5) Equal volumes of hydrochloric acid and sodium hydroxide solutions of the same concentration are mixed and the pH of the resulting solution is checked with a pH paper. What would be the colour obtained?

(a) Red
(b) Yellow
(c) Yellowish green
(d) Blue

Ans: (c)

6) What happens when a solution of an acid is mixed with a solution of a base in a test tube?

(i) The temperature of the solution increases

(ii) The temperature of the solution decreases

(iii) The temperature of the solution remains the same

(iv) Salt formation takes place

(a) (i) only

(b) (i) and (iii)

(d) (i) and (iv)

Ans: (d)

7) An aqueous solution turns red litmus solution blue. Excess addition of which of the following solution would reverse the change?

(a) Baking powder

(b) Lime

(d) Hydrochloric acid

Ans: (d)

8) During the preparation of hydrogen chloride gas on a humid day, the gas is usually passed through the guard tube containing calcium chloride. The role of calcium chloride taken in the guard tube is to

(a) absorb the evolved gas

(b) moisten the gas

d) absorb `Cl^–` ions from the evolved gas

Ans: (c)

9) Which of the following is not a mineral acid?

(a) Hydrochloric acid

(b) Citric acid

(d) Nitric acid

Ans: (b)

10) A solution reacts with zinc granules to give a gas that burns with a 'pop' sound. The solution contains
a) `Mg(OH)_2`

b) `Na_2CO_3`

c) `NaCl`

d) `HCl`

Ans: (d)

11) A solution reacts with marble chips to produce a gas that turns lime-water milky. The solution contains

a) `Na_2SO_4`

b) ` CaSO_4`

c) `H_2SO_4`

d) `K_2SO_4`

Ans: (c)

12) Which of the following gives the correct increasing order of acidic strength

(a) Water < Acetic acid < Hydrochloric acid

(b) Water < Hydrochloric acid < Acetic acid

(d) Hydrochloric acid < Water < Acetic acid

Ans: (a)

13) Which of the following phenomena occur when a small amount of acid is added to water?

a) Ionisation

b) Neutralisation

c) Dilution

d) Salt formation

i) a) and b)

ii) a) and c)

iii) b) and c)

iv) b) and d)

Ans: (ii)

14) Plants require a specific pH range for their healthy growth for most plants, the optimum pH range is from

(a) 5.5 to 7.0

(b) 7.0 to 7.8

(d) 11.5 to 14.0

Ans: (a)

15) Our stomach produces hydrochloric acid acid of pH range

(a) 1.5 to 3.5

(b) 2.1 to 6.0

(d) 3.5 to 4.5

Ans: (a)

16) One of the following is medicine for indigestion. This is

(a) sodium hydroxide

(b) manganese hydroxide

(d) potassium hydroxide

Ans: (c)

17) Tooth decay starts when the pH of the mouth is lower than

(a) 5.5

(b) 7.0

(d) 6.7

Ans: (a)

18) Which of the following salts does not contain water of crystallisation?

(a) Blue vitriol

(b) Baking soda

(d) Gypsum

Ans: (b)

19) Sodium carbonate is a basic salt because it is a salt of

(a) strong acid and strong base

(b) weak acid and weak base

(d) weak acid and strong base

Ans: (D)

20) One of the constituents of baking powder is sodium hydrogen carbonate, the other constituent is

(a) hydrochloric acid

(b) tartaric acid

(d) sulphuric acid

Ans: (b)

21) Which of the following is not salt

(a) Sodium chloride

(b) Slaked lime

(d) Zinc nitrate

Ans: (b)

22) A compound is prepared from gypsum upon heating to a temperature of 373K and it changes back to gypsum on adding water. Which is the incorrect statement about the compound?

(a) The compound is used for setting fractured bones

(b) The compound is called plaster of Paris which is calcium sulphate dihydrate with a formula `CaSO_4. 2H_2O`.

(d) Both (a) and (b).

Ans: (b)

23) Calcium phosphate is present in tooth enamel. Its nature is

(a) basic

(b) acidic

(d) amphoteric

Ans: (b)

24) Common salt besides being used in the kitchen can also be used as the raw material for making

(i) washing soda

(ii) bleaching powder

(iii) baking soda

(iv) slaked lime

(a) (i) and (ii) (b) (i), (ii) and (iv)

Ans: (a)

25) To protect against tooth decay we are advised to brush our teeth regularly. The nature of the toothpaste commonly used is

(a) acidic

(b) neutral

(d) corrosive

Ans: (c)

26) Which of the following is not a mineral acid?

(a) Hydrochloric acid

(b) Citric acid

(d) Nitric acid

Ans: (b)

27) The graph given below depicts a neutralization reaction (acid + alkali → salt + water). The pH of a solution changes as we add excess of acid to an alkali.

Which letter denotes the area of the graph where both acid and salt are present?

(a) A

(b) B

(d) D

Ans: (d)

28) Which of the given options correctly represents the parent acid and base of Calcium Carbonate?

Ans: (B)

29) Vinay observed that the stain of curry on a white shirt becomes reddish-brown when soap is scrubbed on it, but it turns yellow again when the shirt is washed with plenty of water. What might be the reason for his observation?

i. Soap is acidic in nature

ii. Soap is basic in nature

iii. Turmeric is a natural indicator that gives reddish tinge in bases

iv. Turmeric is a natural indicator that gives reddish tinge in acids

(a) i and ii

(b) ii and iii

(d) ii and iv

Ans: (b)

30 Which of the following are present in a dilute aqueous solution of hydrochloric acid?

(a) `H_3O^+ + Cl^–`

(b) `H_3O^+ + OH^–`

(d) unionised `HCl`

Ans: (a)

31. Identify the correct representation of reaction occurring during chloralkali process

(a) `2NaCl(l) + 2H_2O(l) rightarrow 2NaOH(l) + Cl_2(g) + H_2(g)`

(b) `2NaCl(aq) + 2H_2O(aq) rightarrow 2NaOH(aq) + Cl_2(g) + H_2(g)`

(d) `2NaCl (aq) + 2H_2O (l) rightarrow 2NaOH (aq) + Cl_2(g) + H_2(g)`

Ans: (d)

32. Which of the following is(are) true when `HCl (g)` is passed through water?

(i) It does not ionise in the solution as it is a covalent compound.

(ii) It ionises in the solution

(iii) It gives both hydrogen and hydroxyl ion in the solution

(iv) It forms hydronium ion in the solution due to the combination

of hydrogen ion with water molecule

(a) (i) only

(b) (iii) only

(d) (iii) and (iv)

Ans: (c)

33. Match the chemical substances given in Column (A) with their appropriate application given in Column (B)

(a) A—(ii), B—(i), C—(iv), D—(iii)

(b) A—(iii), B—(ii), C—(iv), D—(i)

(d) A—(ii), B—(iv), C—(i), D—(iii)

Ans: (d)

34. In an attempt to demonstrate electrical conductivity through an electrolyte, the following apparatus (Figure ) was set up. Which among the following statement(s) is(are) correct?

(i) Bulb will not glow because electrolyte is not acidic

(ii) Bulb will glow because NaOH is a strong base and furnishes ions for conduction.

(iii) Bulb will not glow because circuit is incomplete

(iv) Bulb will not glow because it depends upon the type of electrolytic solution

(a) (i) and (iii)

(b) (ii) and (iv)

(d) (iv) only

Ans: (c)

35. Sodium hydrogen carbonate when added to acetic acid evolves into 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)

(d) (i) and (iv)

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Case Studies

Frothing in the Yamuna:

The primary reason behind the formation of the toxic foam is the high phosphate content in the wastewater because of detergents used in dyeing industries, dhobi ghat Yamuna's pollution level is so bad that parts of it have been labelled 'dead' as there is no oxygen in it for aquatic life to survive.

1. Predict the pH value of the water of river Yamuna if the reason for froth is the high content of detergents dissolved in it.

a) `10 -11`

b) `5 -7`

c) `2 -5`

d) 7

2. Which of the following statements is correct for the water with detergents dissolved in it?

a) low concentration of hydroxide ion `(OH^- )` and high concentration of hydronium ion `(H_3O^+)`

b) high concentration of hydroxide ion `(OH^- )` and low concentration of hydronium ion `(H_3O^+)`

c) high concentration of hydroxide ion `(OH^-)` as well as hydronium ion `(H_3O^+)`

d) equal concentration of both hydroxide ion `(OH^-)` and hydronium ion `(H_3O^+)`.

3. The table provides the pH value of four solutions P, Q, R and S

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`

4. High content of phosphate ion in river Yamuna may lead to:

a) decreased level of dissolved oxygen and increased growth of algae

b) decreased level of dissolved oxygen and no effect of the growth of algae

c) increased level of dissolved oxygen and increased growth of algae

d) decreased level of dissolved oxygen and decreased growth of algae

5. If a sample of water containing detergents is provided to you, which of the following methods will you adopt to neutralize it?

a) Treating the water with baking soda

b) Treating the water with vinegar

c) Treating the water with caustic soda

d) Treating the water with washing soda

Answer:

1 (a)

2 (b)

3 (c)

4 (a)

5 (b)

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Q. Fill in the missing data in the following table

Q) When pH of rainwater is less than 5.6, it is called ................

Q) 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?

Q) a) `Zn + HNO_3 \rightarrow` ............................
b) `Zn + CH_3COOH \rightarrow` .......................

c) `Zn + HCl \rightarrow` ....................

Q) 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?

Q) 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.

Q) A student prepared solutions of (i) an acid and (ii) a base in two separate beakers. She forgot to label the solutions and litmus paper is not available in the laboratory. Since both the solutions are colourless, how will she distinguish between the two?

Q) In the following schematic diagram for the preparation of hydrogen gas as shown in Figure, what would happen if following changes are made?

(a) In place of zinc granules, the same amount of zinc dust is taken in the test tube

(b) Instead of dilute sulphuric acid, dilute hydrochloric acid is taken.

(d) Sodium hydroxide is taken in place of dilute sulphuric acid and the tube is heated.

Q) Identify the compound X on the basis of the reactions given below. Also, write the name and chemical formulae of A, B, and C.

Ans 👉 `2NaOH (aq) + Zn (S) \rightarrow Na_2ZnO_2 (s) + H_2 (g)`

`NaOH (aq) + HCl (aq) \rightarrow NaCl (aq) + H_2O (l)`

`NaOH (aq) + CH_3COOH (aq) \rightarrow CH_3COONa (aq) + H_2O (l)`

`\therefore` compound A, B, and C are Sodium zincate `(Na_2ZnO_2)`, Sodium chloride `(NaCl)` and Sodium acetate `(CH_3COONa)` . Compound X is Sodium hydroxide `(NaOH)`.

Q) 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 `HCl` solution (the same solution as before) required to neutralise it will be.....................

Q) A solution reacts with crushed eggshells to give a gas that turns lime-water milky. The solution contains..........................

Q) When a piece of limestone reacts with dilute HCl, a gas X is produced. When gas X is passed through lime water then a white precipitate Y is formed. On passing excess of gas X, the white precipitate dissolves forming a soluble compound Z.
a) What are X, Y, Z?

b) Write the equations for the reactions which take place:

i) when limestone reacts with dilute HCL

ii) when gas X reacts with lime water to form white precipitate Y.

iii) when the excess of gas X dissolves with white precipitate Y to form a soluble compound Z.

Ans 👉 Limestone reacts with dilute `HCl` then Calcium chloride, Carbon dioxide and Water formed.

`CaCO_3 + 2HCl \rightarrow CaCl_2 + CO_2 + H_2O`

When Carbon dioxide (gas X) is passed through lime water then a Calcium carbonate ( white precipitate Y) is formed.

`Ca(OH)_2 + CO_2 \rightarrow CaCO_3 + H_2O`

On passing excess carbon dioxide the following reaction takes place, the white precipitate formed first dissolves due to the formation of a soluble salt calcium hydrogen carbonate.

`CaCO_3 + H_2O + CO_2 \rightarrow Ca(HCO_3)_2`

`\therefore` the compounds X, Y and Z are carbon dioxide gas, calcium carbonate and calcium hydrogen carbonate

Q) Why do `HCl`, `HNO_3`, etc., show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character?

Q) Why does an aqueous solution of acid conduct electricity?

Q) Why does distilled water not conduct electricity, whereas rainwater does?

Q) Compounds such as alcohols and glucose also contain hydrogen but are not categorised as acids. Describe an Activity to prove it.

Q) In an attempt to demonstrate electrical conductivity through an electrolyte, the following apparatus was set up. Which among the following statement(s) is(are) correct?

(i) Bulb will not glow because the electrolyte is not acidic

(ii) Bulb will glow because NaOH is a strong base and furnishes ions for conduction.

(iii) Bulb will not glow because the circuit is incomplete

(iv) Bulb will not glow because it depends upon the type of electrolytic solution

(a) (i) and (iii)

(b) (ii) and (iv)

(d) (iv) only

Q) Which of the following are present in a dilute aqueous solution of hydrochloric acid?

(a) `H_3O^+ + Cl^–`

(b) `H_3O^+ + OH^–`

(d) unionised HCl

Q) Why does dry HCl gas not change the colour of the dry litmus paper?

Q) While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?

Q) How is the concentration of hydronium ions `(H_3O^+)` affected when a solution of an acid is diluted?

Q. For making cake, baking powder is taken. If at home your mother uses baking soda instead of baking powder in cake,

(a) how will it affect the taste of the cake and why?

(b) how can baking soda be converted into baking powder?

Ans 👉(a) Baking soda is sodium hydrogencarbonate. On heating, it is converted into sodium carbonate which is bitter to taste

`2NaHCO_3 \overset{\triangle}{\rightarrow} Na_2CO_3 + H_2O + CO_2`

(b) Baking soda can be converted into baking powder by the addition of appropriate amount of tartaric acid to it.

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