Free Acids, Bases and Salts MCQs with Answers

281. Soda ash has the chemical formula:

• A. NaHCO3
• B. NaCO3
• C. Na2CO3
• D. Ca(OH)2

Explanation: The explanation for this question will be added soon.

282. A solid compound dissolves readily in water to give a weakly alkaline solution. On evaporation of the water, X was recovered unchanged. Which one of the following could be X?

• A. CH3 NH3 Cl
• B. CH3 O- Na+
• C. C6H5 O-Na+
• D. C6H5NH2
• E. H2NCH2CO2H

Explanation: The sodium salt of phenol, which is weakly acidic. When dissolved in water, it would give a weakly alkaline solution due to the hydrolysis of the phenoxide ion. On evaporation, we would recover the original compound unchanged.

283. Addition of 2% gypsum in cement leads to:

• A. Hydration
• B. Hydrolysis
• C. Preventing of rapid hardening
• D. All of the above options are correct

Explanation: During the grinding there is added about 2% of gypsum which prevents the cement from hardening too rapidly.The addition of gypsum increases the setting time of cement.

284. Sulphuric acid is used to manufacture:

• A. HCL and HN03.
• B. H3P04.
• C. Both A and B
• D. Both HCI and 2COOH.

Explanation: Concentrated sulphuric acid has a high boiling point (356°C). So, it is considered to be non-volatile. Hence, it is used for preparing volatile acids like Hydrochloric acid and Nitric acids from their salts by double decomposition.

285. The protonation of carboxylic acid is:

• A. Option A
• B. Option B
• C. Option C
• D. Option D

Explanation: Explanation:During protonation, the double bond between the carbon and oxygen is broken. As a result, a long pair is present on the oxygen atom as a result hydrogen ion can form the bond with it. Thus the correct option is B.

286. The chemical substance, when dissolved in water, gives "H+" is called:

• A. Acid
• B. Base
• C. Amphoteric
• D. Neutral

Explanation: Acids are substances that release hydrogen ions (H+) when dissolved in water. They have a pH value less than 7 and can react with bases to form salts.

287. Which one of the following is the correct equation of 1st ionization of sulphuric acid?

• A. H2SO4(aq) + H2O(l) --> H+ + SO42-
• B. H2SO4(aq) + H2O(l) --> H+(aq) + HSO4-
• C. H2SO4(aq) + H2O(l) --> 2H+ + SO42-
• D. H2SO4(aq) + H2O(l) --> H3O+ + SO42-

Explanation: The 1st ionisation equation involves dissociation of 1 H+ ion from H2SO4, followed by second H+ dissociation in the second ionisation.

288. Which material possesses the highest pH?

• A. Soft drinks
• B. Bananas
• C. Milk of magnesia
• D. Sea water

Explanation: The basic pH of milk of magnesia helps neutralize overactive stomach acids that cause heartburn.

289. 0.1 mole of acetic acid has been dissolved per dm3 of the solution, the percentage ionization of acetic acid will be

• A. 13
• B. 15
• C. 1.3
• D. 0.1

Explanation: A, B and D are incorrect because these are not correct percentage ionization valuesC is correct since The solution is given as CH3COOH dissociates to a small extent:CH3COOH ↔ CH3COO- + H+Calculate [H+] from the Ka equation.Ka = [H+] [[CH3COO-] / [CH3COOH]Because [H+] =[CH3COO-] and dissociation is very small, we can write the equation asKa = [H+]² / 0.1Ka = 1.8*10-51.8*10-5 = [H+]² / 0.1[H+]² = (1.8*10-5)* 0.1[H+]² = 1.8*10-6[H+] = 0.0013M% dissociation = 0.0013/0.1*100 = 1.34%

290. The 'pH' of human blood is:

• A. 6.7 - 8
• B. 7.9
• C. 7.5
• D. 7.35 - 7.4

Explanation: The pH of human blood is typically around 7.35 to 7.45, which is slightly alkaline or basic. It is important for the pH of blood to remain within this narrow range as deviations can have adverse effects on bodily functions.