Environmental Chemistry – NDA Chemistry PYQs

Q1. NDA 2010-I
Match List I with List II:
A. Ozone gas — 1. Combines with haemoglobin
B. Nitrous oxide — 2. Ultraviolet radiation
C. Carbon dioxide — 3. Component of air in small quantity
D. Carbon monoxide — 4. Visible radiation; 5. Infrared radiation
(a) A-1, B-4, C-5, D-3 (b) A-2, B-3, C-5, D-1 (c) A-4, B-4, C-3, D-2 (d) A-2, B-5, C-3, D-1
Answer: (b) A-2, B-3, C-5, D-1
Ozone shields the Earth from ultraviolet radiation (A-2). Nitrous oxide (N₂O) is a component of air in small quantities (B-3). Carbon dioxide absorbs infrared radiation and contributes to the greenhouse effect (C-5). Carbon monoxide combines with haemoglobin and blocks oxygen transport (D-1).

Q2. NDA 2011-I
Which one among the following methods is NOT effective in removing arsenic from contaminated groundwater?
(a) Boiling (b) Reverse osmosis (c) Ion exchange (d) Coagulation-adsorption
Answer: (a) Boiling
Arsenic is a dissolved chemical contaminant, not a biological one. Boiling water kills bacteria and viruses but cannot remove dissolved arsenic salts. Reverse osmosis, ion exchange, and coagulation-adsorption all physically remove dissolved arsenic from water.