2. Acids, Bases and Salts

SEBA Class 10 Science Chapter 2. Acids, Bases and Salts

Chapter 2. Acids, Bases and Salts

Class 10 Science Multiple Choice Questions and Answers :

Question : A solution turns red litmus blue, its pH is likely to be [SEBA 2016,2018,2021]
(a) 1 (b) 4 (c) 5 (d) 10

Answer: (d) 10
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) HCl
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 HCl solution (the same solution as before) required to neutralise it will be : [SEBA 2020]
(a) 4 mL (b) 8 mL (c) 12 mL (d) 16 mL

Answer: (d) 16mL

[ Hint: 10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a solution HCl .

So, 20 mL of a solution of NaOH is found to be completely neutralised by = 2 × 8 mL = 16 mL of a solution HCl . ]
Question : Which one of the following types of medicines is used for treating indigestion? [SEBA 2017]
(a) Antibiotic
(b) Analgesic
(c) Antacid
(d) Antiseptic

Answer: (c) Antacid .

[ The type of medicine used for treating indigestion is an antacid. ]

Question : Which of the following compound is used in soda – acid fire extinguisher ? [SEBA 2023]

(a) (b) (c) (d)

Answer : (c)

[ is used in soda-acid fire extinguishers.]

Question : 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)

Answer : (d) (i) and (iv)

[ When a solution of an acid is mixed with a solution of a base, a chemical reaction called neutralization occurs. In this reaction, the acid and base react to form water and a salt. The temperature change during the reaction depends on the specific acid and base involved, but generally, the reaction is exothermic, meaning it releases heat.]

Question : 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

Answer : (d) Hydrochloric acid

[ Hydrochloric acid is an acidic solution, and adding it in excess can neutralize the base present in the solution, turning it acidic and reversing the color change of the litmus solution from blue back to red.]

Question : 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 ions from the evolved gas

Answer : (c) absorb moisture from the gas

[ The role of calcium chloride in the guard tube is to absorb moisture from the hydrogen chloride gas. Calcium chloride is a hygroscopic substance, meaning it has a strong affinity for water and can absorb moisture from the surrounding air or gases. In this case, it helps to dry the hydrogen chloride gas by removing any water vapor present in it during its preparation on a humid day. This ensures that the hydrogen chloride gas collected is dry and free from moisture. ]

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

(a) Blue vitriol

(b) Baking soda

(d) Gypsum

Answer : (b) Baking soda.

[ Baking soda (sodium bicarbonate, NaHCO₃) does not contain water of crystallization. It is a hydrate, but the water is not present in a fixed ratio as water of crystallization. Blue vitriol (copper sulfate pentahydrate, CuSO₄ · 5H₂O), washing soda (sodium carbonate decahydrate, Na₂CO₃ · 10H₂O), and gypsum (calcium sulfate dihydrate, CaSO₄ · 2H₂O) all contain water of crystallization in their structures. ]

Question : 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

Answer : (d) weak acid and strong base

[ Sodium carbonate (Na₂CO₃) is a basic salt because it is a salt of a weak acid (carbonic acid, H₂CO₃) and a strong base (sodium hydroxide, NaOH). ]

Question : Calcium phosphate is present in tooth enamel. Its nature is

(a) basic

(b) acidic

(d) amphoteric

Answer : (a) basic

[ In the case of tooth enamel, calcium phosphate tends to act as a basic substance, helping to neutralize acids and maintain the pH balance in the mouth. ]

Question : 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

Answer : (d) An antacid

[ Antacids are substances that are often basic and are used to neutralize excess stomach acid. Therefore, adding an antacid to the solution would likely change the color of the pH paper to greenish-blue. ]

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

(d) Hydrochloric acid < Water < Acetic acid

Answer : (b) Water < Hydrochloric acid < Acetic acid

[ In this order, water is neutral, hydrochloric acid is a strong acid, and acetic acid is a weak acid. ]

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 hydrogencarbonate

(d) Neutralise the acid with a strong alkali

Answer : (b) Wash the hand immediately with plenty of water and apply a paste of sodium hydrogen carbonate

[ In case of a spill of concentrated acid on the skin, it is important to immediately wash the affected area with plenty of water to dilute and remove the acid. The use of sodium hydrogen carbonate (baking soda) in the paste can help neutralize any remaining acid. Sodium hydrogen carbonate is a mild base that can react with the acid, forming water and a salt. This can be an effective first aid measure in dealing with acid spills on the skin. ]

Question : 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)

Answer : (a) (i) and (ii)

[ When sodium hydrogencarbonate (baking soda) is added to acetic acid, it undergoes a chemical reaction, producing carbon dioxide gas.

(i) It turns lime water milky - True. The evolved carbon dioxide reacts with lime water (calcium hydroxide) to form calcium carbonate, which is insoluble and gives a milky appearance.

(ii) It extinguishes a burning splinter - True. Carbon dioxide is not combustible and can extinguish a burning splinter by displacing oxygen. ]

Question : 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)

Answer : (a) (i) and (ii)

[ Common salt (sodium chloride, NaCl) can be used as a raw material for making: (i) washing soda (sodium carbonate, Na₂CO₃) (ii) bleaching powder (calcium oxychloride, Ca(OCl)₂) ]

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

(a) hydrochloric acid

(b) tartaric acid

(d) sulphuric acid

Answer : (b) tartaric acid

[ Tartaric acid is a common acid used in baking powder to react with sodium hydrogencarbonate and produce carbon dioxide gas, contributing to the leavening process in baking.]

Question : 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

(d) corrosive

Answer : (c) basic

[ Toothpaste commonly used is slightly basic or alkaline in nature. The alkalinity helps in neutralizing acids produced by bacteria in the mouth, which can contribute to tooth decay. ]

Question : 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)

Answer : (d) (ii) and (iv)

[ (ii) Higher the pH, weaker the acid. (iv) Lower the pH, weaker the base.

The pH scale is a measure of the acidity or basicity of a solution. Lower pH values indicate stronger acids, while higher pH values indicate weaker acids. On the other hand, higher pH values indicate stronger bases, while lower pH values indicate weaker bases. ]

Question : The pH of the gastric juices released during digestion is

(a) less than 7

(b) more than 7

(d) equal to 0

Answer : (a) less than 7

[ The pH of gastric juices released during digestion is generally less than 7. The gastric juice in the stomach is acidic, and its pH is typically around 1.5 to 3.5.]

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)

Answer : (b) (i) and (iii)

[ (i) Acids ionize in water to produce hydronium ions (H₃O⁺) and the conjugate base.

(iii) The acid is diluted as it mixes with water, resulting in a less concentrated solution. ]

Question : Which one of the following can be used as an acid–base indicator by a visually impared student?

(a) Litmus

(b) Turmeric

(d) Petunia leaves

Answer : (c) Vanilla essence

[ Vanilla essence can be used as an acid-base indicator by a visually impaired student. Vanilla essence is sensitive to pH changes and can exhibit different smells under acidic and basic conditions. It has a sweet aroma in a basic (alkaline) solution and a slightly bitter aroma in an acidic solution. ]

Question : Which of the following substance will not give carbon dioxide on treatment with dilute acid?

(a) Marble

(b) Limestone

(d) Lime

Answer : (d) Lime

[ lime (calcium oxide, CaO) will not produce carbon dioxide when treated with dilute acid because it is already an oxide and does not contain carbonate ions. ]

Question : Which of the following is acidic in nature?

(a) Lime juice

(b) Human blood

(d) Antacid

Answer : (a) Lime juice

[ Lime juice is acidic in nature. It contains citric acid, which imparts a sour taste to the juice. ]

Question : Which of the following is not a mineral acid?

(a) Hydrochloric acid

(b) Citric acid

(d) Nitric acid

Answer : (b) Citric acid

[ Citric acid is not a mineral acid. It is an organic acid found naturally in citrus fruits like lemons and oranges. ]

Question : Which among the following is not a base?

(a) NaOH

(b) KOH

(c)

(d)

Answer : (d)

[ , also known as ethanol, is not a base. It is an alcohol. ]

Question : Which of the following statements is not correct?

(a) All metal carbonates react with acid to give a salt, water and carbon dioxide

(b) All metal oxides react with water to give salt and acid

(d) Some non metal oxides react with water to form an acid

Answer : (b) All metal oxides react with water to give salt and acid

[ Metal oxides typically react with water to form metal hydroxides (alkaline solutions) and not salts and acids. The correct reaction is: Metal oxide+Water→Metal hydroxide ]

Question : Match the chemical substances given in Column (A) with their appropriate application given in Column (B)

Column (A)	Column (B)
(A) Bleaching powder	(i) Preparation of glass
(B) Baking soda	(ii) Production of and
(C) Washing soda	(iii) Decolourisation
(D) Sodium chloride	(iv) Antacid

(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)

Answer : (c) A—(iii), B—(iv), C—(i), D—(ii)

[ (A) Bleaching powder is used for decolourisation (iii).

(B) Baking soda is used as an antacid (iv).

(D) Sodium chloride is not directly matched in the given options, but its common uses include seasoning in food. ]

Question : Equal volumes of hydrochloric acid and sodium hydroxide solutions of same concentration are mixed and the pH of the resulting solution is checked with a pH paper. What would be the colour obtained? (You may use colour guide given in Figure 2.2

(a) Red

(b) Yellow

(d) Blue

Answer : (c) Yellowish green

[ The mixing of equal volumes of hydrochloric acid (HCl) and sodium hydroxide (NaOH) solutions of the same concentration results in a neutralization reaction, forming water and a salt. The pH of the resulting solution should be close to 7, making it neutral. ]

Question : 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

Answer : (c) (ii) and (iv)

[ (ii) It ionises in the solution (iv) It forms hydronium ion in the solution due to the combination of hydrogen ion with water molecule

When hydrogen chloride (HCl) gas is passed through water, it dissolves and undergoes ionization in the solution. The ionization leads to the formation of hydronium ions (H₃O⁺), which is a combination of hydrogen ions (H⁺) and water molecules. ]

Question : Which of the following statements is true for acids?

(a) Bitter and change red litmus to blue

(b) Sour and change red litmus to blue

(d) Bitter and change blue litmus to red

Answer : (c) Sour and change blue litmus to red .

[ The correct statement for acids is that they are sour in taste and change the color of blue litmus paper to red. ]

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

(a)

(b)

(c)

(d) unionised HCl

Answer : (a)

[ In a dilute aqueous solution of hydrochloric acid (HCl), the predominant species are ions formed due to the dissociation of the acid. Hydrochloric acid dissociates into hydrogen ions() and chloride ions ()in water. ]

Question : Identify the correct representation of reaction occurring during chloralkali process

(a)

(b)

(c)

(d)

Answer : (d)

[ This represents the electrolysis of sodium chloride (NaCl) in aqueous solution, resulting in the formation of sodium hydroxide (NaOH), chlorine gas (), and hydrogen gas (). ]