Railway Science (Chemistry-Chemistry in Everyday life)

61. Fill in the blank with the most appropriate option. [RRB ALP Tier - I (21/08/2018) Afternoon]

(a) make it unsuitable for drinking
(b) make it suitable as an antiseptic
(c) increase its stability
(d) make it suitable for drinking

Correct Answer: (a) make it unsuitable for drinking

Solution:

Denatured alcohol refers to alcohol products adulterated with toxic and/or bad tasting additives (e.g., methanol, benzene, pyridine, castor oil, gasoline, isopropyl alcohol, and acetone), making it unsuitable for human consumption; It is used as a lower-cost solvent or fuel for home-scale or industrial use.

62. Which of the following is used in the preparation of vinegar ? [RRB ALP Tier - I (29/08/2018) Evening]

(a) Ethanoic acid
(b) Ethanol
(c) Methanol
(d) Acetic acid

Correct Answer: (d) Acetic acid

Solution:

Properties - colorless, hygroscopic liquid, has a pungent smell, taste is sour. Other uses of Acetic acid - pickled vegetables, sauce, as a raw material for spice.
Uses of Ethanoic acid - production of synthetic fibers, formation of esters in perfume-making process.
Uses of Ethanol - Fuels, Medicines, Preservatives, Preparation of organic compounds. Uses of Methanol - automotive antifreezes, in rocket fuels, and as a general solvent.

63. Is Baking soda chemically different from Baking powder ? [RRB ALP Tier - I (29/08/2018) Evening]

(a) Yes, Baking soda is Sodium bicarbonate while Baking powder is Calcium Carbonate.
(b) Yes, Baking soda is Sodium bicarbonate while Baking powder is a mixture of Sodium bicarbonate and Tartaric acid.
(c) No, they are identical chemically.
(d) Yes, Baking soda is Sodium Carbonate while Baking powder is Sodium Bicarbonate.

Correct Answer: (b) Yes, Baking soda is Sodium bicarbonate while Baking powder is a mixture of Sodium bicarbonate and Tartaric acid.

Solution:

Solvay process is used for the production of sodium carbonate. Baking Soda [Sodium hydrogen carbonate (NaHCO₃)] is prepared when Sodium Chloride is reacted with water along with Ammonia (NH₃) and carbon dioxide. NaCl + H₂O + CO₂ + NH₃ → NaHCO₃ + NH₄Cl.
Uses of baking Soda - Reduces the acidity, making cakes, bread, cold drinks, fire extinguishers, etc. When Baking Soda is mixed with mild acid like tartaric acid in the presence of water or carbon dioxide, get Baking Powder. NaHCO₃ + H⁺ → H₂O + CO₂ + Sodium Acid Salt.