Chapter 2 – Acids, Bases And Salts

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)
• (c)(ii) and (iii)
• (d)(i) and (iv)

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
• (c)Ammonium hydroxide solution
• (d)Hydrochloric acid

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
• (c)absorb moisture from the gas
• (d)absorb Cl– ions from the evolved gas

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

• (a)Blue vitriol
• (b)Baking soda
• (c)Washing soda
• (d)Gypsum

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

• (a)strong acid and strong base
• (b)weak acid and weak base
• (c)strong acid and weak base
• (d)weak acid and strong base

Calcium phosphate is present in tooth enamel. Its nature is

• (a)basic
• (b)acidic
• (c)neutral
• (d)amphoteric

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
• (c)Common salt
• (d)An antacid

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

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 hydrogencarbonate
• (c)After washing with plenty of water apply solution of sodium hydroxide on the hand
• (d)Neutralise the acid with a strong alkali

Sodium hydrogencarbonate 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) 10 E XEMPLAR P ROBLEMS – SCIENCE

Common salt besides being used in 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)
• (c)(i) and (iii)
• (d)(i), (iii) and (iv)

One of the constituents of baking powder is sodium hydrogencarbonate, the other constituent is

• (a)hydrochloric acid
• (b)tartaric acid
• (c)acetic acid
• (d)sulphuric acid

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

• (a)acidic
• (b)neutral
• (c)basic
• (d)corrosive

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)
• (c)(i) and (iv)
• (d)(ii) and (iv)

The pH of the gastric juices released during digestion is

• (a)less than 7
• (b)more than 7
• (c)equal to 7
• (d)equal to 0

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

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• (a)(i) and (ii)
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Match the acids given in Column (A) with their correct source given in Column (B) Column (A) Column (B) (a) Lactic acid

• (i)Tomato (b) Acetic acid
• (ii)Lemon (c) Citric acid
• (iii)Vinegar (d) Oxalic acid
• (iv)Curd

Match the important chemicals given in Column (A) with the chemical formulae given in Column (B) Column (A) Column (B) (a) Plaster of Paris

• (i)Ca(OH)2 (b) Gypsum
• (ii)CaSO4.1/2 H2O (c) Bleaching Powder
• (iii)CaSO4.2H2O (d) Slaked Lime
• (iv)Ca(ClO)2

What will be the action of the following substances on litmus paper? Dry HCl gas, Moistened NH3 gas, Lemon juice, Carbonated soft drink, Curd, Soap solution.

Name the acid present in ant sting and give its chemical formula. Also give the common method to get relief from the discomfort caused by the ant sting.

What happens when nitric acid is added to egg shell?

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?

How would you distinguish between baking powder and washing soda by heating?

Salt A commonly used in bakery products on heating gets converted into another salt B which itself is used for removal of hardness of water and a gas C is evolved. The gas C when passed through lime water, turns it milky. Identify A, B and C. ACIDS, BASES AND SALTS 15

In one of the industrial processes used for manufacture of sodium hydroxide, a gas X is formed as by product. The gas X reacts with lime water to give a compound Y which is used as a bleaching agent in chemical industry. Identify X and Y giving the chemical equation of the reactions involved.

Fill in the missing data in the following table Salt obtained from Name of the salt Formula Base Acid

• (i)Ammonium chloride NH4Cl NH4OH —
• (ii)Copper sulphate — — H2SO4
• (iii)Sodium chloride NaCl NaOH —
• (iv)Magnesium nitrate Mg (NO3)2 — HNO3 (v) Potassium sulphate K2SO4 — — (vi) Calcium nitrate Ca(NO3)2 Ca(OH)2 —

What are strong and weak acids? In the following list of acids, separate strong acids from weak acids. Hydrochloric acid, citric acid, acetic acid, nitric acid, formic acid, sulphuric acid.

When zinc metal is treated with a dilute solution of a strong acid, a gas is evolved, which is utilised in the hydrogenation of oil. Name the gas evolved. Write the chemical equation of the reaction involved and also write a test to detect the gas formed. .QPI #PUYGT 3WGUVKQPU

In the following schematic diagram for the preparation of hydrogen gas as shown in Figure 2.3, what would happen if following changes are made? Delivery tube Stand Burning of hydrogen gas with a pop sound Candle Test tube Hydrogen Dilute gas sulphuric bubbles acid Soap bubble filled Zinc granules with hydrogen Soap solution Fig. 2.3 16 E XEMPLAR P ROBLEMS – SCIENCE

This question refers to a figure in the original PDF.

• (a)In place of zinc granules, same amount of zinc dust is taken in the test tube
• (b)Instead of dilute sulphuric acid, dilute hydrochloric acid is taken
• (c)In place of zinc, copper turnings are taken
• (d)Sodium hydroxide is taken in place of dilute sulphuric acid and the tube is heated.

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?
• (c)what is the role of tartaric acid added to baking soda?

A metal carbonate X on reacting with an acid gives a gas which when passed through a solution Y gives the carbonate back. On the other hand, a gas G that is obtained at anode during electrolysis of brine is passed on dry Y, it gives a compound Z, used for disinfecting drinking water. Identity X, Y, G and Z.

A dry pellet of a common base B, when kept in open absorbs moisture and turns sticky. The compound is also a by–product of chloralkali process. Identify B. What type of reaction occurs when B is treated with an acidic oxide? Write a balanced chemical equation for one such solution.

A sulphate salt of Group 2 element of the Periodic Table is a white, soft substance, which can be moulded into different shapes by making its dough. When this compound is left in open for some time, it becomes a solid mass and cannot be used for moulding purposes. Identify the sulphate salt and why does it show such a behaviour? Give the reaction involved.

Identify the compound X on the basis of the reactions given below. Also, write the name and chemical formulae of A, B and C. Fig. 2.4 ACIDS, BASES AND SALTS 17

This question refers to a figure in the original PDF.