Free Acids, Bases and Salts MCQs with Answers

61. The dilute solution of _ is called vinegar.

• A. Formic acid
• B. Oxalic acid
• C. Benzoic acid
• D. Acetic acid

Explanation: A dilute (approximately 5 percent by volume) solution of acetic acid produced by fermentation and oxidation of natural carbohydrates is called vinegar.

62. Which of the following acids is used for etching glass?

• A. Hydrochloric Acid
• B. Nitric Acid
• C. Hydrofluoric Acid
• D. Sulphuric Acid
• E. Acetic Acid

Explanation: HF etching is capable of etching materials such as amorphous silicon dioxide; quartz and glass at very high etch rates. Since HF etching is a wet process, meaning that it uses chemicals, it creates an isotropic etch. This means that there are curved etched out sections under the etching mask.

63. H2SO4 has great affinity for water because:

• A. It decomposes the acid
• B. It hydrolyses the acid
• C. Acid decomposes the water
• D. Acid forms hydrates with water

Explanation: Sulphuric acid is kept in air-tight bottles because if kept in the open it absorbs water vapors from the surrounding. It is a dehydrating agent. Sulphuric acid forms hydrate with water because the reaction of water and acid is highly exothermic and a great amount of heat in the form of fumes is liberated in that exothermic reaction of acid and water, acid produces stable hydrates-this shows the acid's affinity for water.

64. Methyl orange is _ in acidic solutions.

• A. Yellow
• B. Pink
• C. Orange
• D. Red

Explanation: Methyl orange is orange in colour. It is used in laboratories to determine if a solution is acidic or basic. In acidic medium, it gives red colour and in basic medium, it gives yellow colour.

65. Farming salt is:

• A. NaCl
• B. HF
• C. KHF2
• D. KClO3

Explanation: NaCl is an ionic compound, also known as common salt or farming salt used in cooking.

66. Blue litmus turns red in a solution of pH:

• A. Below 7
• B. 7
• C. Above 7
• D. At all pH

Explanation: Blue litmus paper turns red under acidic conditions (pH of below 7)

67. The basicity of H3PO4 is:

• A. 1
• B. 2
• C. 3
• D. 4

Explanation: Basicity means the number of replaceable hydrogen atoms. H3PO4 = 3H+ + PO4- For hydrogen to be acidic, it must be attached to a strongly electronegative atom. Here it is attached to 3 oxygen. Hence the basicity of H3PO4 is 3.

68. Acidic buffer consists of:

• A. Strong acid and salt of it with a weak base
• B. Weak acid and salt of it with a strong base
• C. Strong acid and salt of it with a strong base
• D. Weak acid and salt of it with a weak base

Explanation: The formation of a buffer solution requires a weak base OR a weak acid with its salt with a strong acid OR a strong base respectively, which is only stated in option B. A and C are incorrect because strong acid with its salt does not form a buffer solution; weak acids with its salt forms a buffer solution. D is theoretically not possible because a weak acid can not react with a weak base to form a salt.

69. The pH of human blood is maintained between:

• A. 7.35 to 7.45
• B. 7.55 to 7.65
• C. 7.00 to 7.25
• D. 7.85 to 7.95

Explanation: Blood is normally slightly basic, with a normal pH range of about 7.35 to 7.45. Usually, the body maintains the pH of blood close to 7.40. This is because most enzymes present in the blood have their optimum pH in this range.

70. The buffer solution is not formed for:

• A. NH4OH + NH4Cl
• B. CH3COOH + CH3COONa
• C. C6H5COOH + C6H5COONa
• D. HCl + NaCl

Explanation: For the formation of a buffer, there should be a weak acid OR a weak base together with its salt. Since option D has a strong acid (HCl) and its salt (NaCl), a buffer solution can not be formed with this combination. Option A has a weak base and its salt. Options B and C have weak acids and their salts. These combinations can form buffer solutions so, they are not correct options.