CUET-PG — Environmental Sciences · India · National Testing Agency
Original practice questions written to the published syllabus · not past papersThe chemistry of water, soil and air that pollution, treatment and climate subjects assume: equilibria, the carbonate system, redox, gas solubility, ozone and smog chemistry. GATE ES Section 2 in full.
In the exams: GATE ES Section 2; UGC NET Environmental Sciences Unit 2; ICAR AIEEA-PG Physical Science Unit II (chemistry)
CUET-PG Environmental Sciences and CSIR-UGC NET (Earth, Atmospheric, Ocean and Planetary Sciences)
Carbonate chemistry and ocean acidification, atmospheric composition and ozone chemistry, and basic equilibrium and redox principles.
How our questions for CUET-PG spread across the units of Environmental Chemistry. Difficulty: 16 easy, 20 medium, 0 hard.
| Chemical bonding, concentration units, activity and ionic strength | 5 | |
| Acid-base equilibria, buffers and alkalinity | 4 | |
| Chemical equilibrium, thermodynamics and reaction kinetics | 3 | |
| The carbonate system and ocean acidification | 3 | |
| Solubility of gases in water: Henry's law | 3 | |
| Complexation, precipitation and solubility product | 3 | |
| Redox reactions, pe-pH diagrams and redox zonation | 3 | |
| Water quality parameters and their measurement | 3 | |
| Radioactivity and radionuclides in the environment | 3 | |
| Speciation of inorganic and organic contaminants | 2 | |
| Composition and structure of the atmosphere | 2 | |
| Tropospheric ozone and photochemical smog | 1 | |
| Stratospheric ozone chemistry and ozone-depleting substances | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
What is the ionic strength of a 0.01 M CaCl2 solution?
A. 0.03 M
I = ½(0.01 × 2² + 0.02 × 1²) = ½(0.04 + 0.02) = 0.03 M. 0.01 is the salt concentration; 0.02 ignores charge squared for Ca; 0.05 omits the ½.
Further reading: See the manual sources: Sawyer, McCarty & Parkin; Manahan; Stumm & Morgan; Seinfeld & Pandis; IS 10500; WMO/UNEP ozone assessment
An acetate buffer contains 0.2 M acetate and 0.1 M acetic acid (pKa 4.76). What is its pH?
B. 5.06
pH = pKa + log([A⁻]/[HA]) = 4.76 + log 2 = 5.06. 4.76 assumes equal amounts; 4.46 inverts the ratio; 5.76 adds one full unit.
Further reading: See the manual sources: Sawyer, McCarty & Parkin; Manahan; Stumm & Morgan; Seinfeld & Pandis; IS 10500; WMO/UNEP ozone assessment
How does the saturation concentration of dissolved oxygen in water change as temperature rises?
D. It decreases
Gas solubility falls with temperature: about 14.6 mg/L at 0 °C, 9.1 at 20 °C and 7.6 at 30 °C.
Further reading: See the manual sources: Sawyer, McCarty & Parkin; Manahan; Stumm & Morgan; Seinfeld & Pandis; IS 10500; WMO/UNEP ozone assessment
Why do amphoteric metal hydroxides such as Al(OH)3 redissolve at very high pH?
D. They form soluble hydroxo-anions such as aluminate
Amphoteric hydroxides dissolve in strong base as aluminate and similar anions, so each metal has a pH of minimum solubility.
Further reading: See the manual sources: Sawyer, McCarty & Parkin; Manahan; Stumm & Morgan; Seinfeld & Pandis; IS 10500; WMO/UNEP ozone assessment
On a pe–pH diagram for iron, which form is stable under oxidising, near-neutral conditions?
A. Insoluble ferric oxyhydroxides
Oxidising, neutral conditions favour Fe(III) solids; reducing or acidic conditions favour soluble Fe²⁺.
Further reading: See the manual sources: Sawyer, McCarty & Parkin; Manahan; Stumm & Morgan; Seinfeld & Pandis; IS 10500; WMO/UNEP ozone assessment
What is the oxidation state of sulphur in sulphate (SO4²⁻)?
B. +6
S + 4(−2) = −2, so S = +6. Sulphide is −2; sulphite +4.
Further reading: See the manual sources: Sawyer, McCarty & Parkin; Manahan; Stumm & Morgan; Seinfeld & Pandis; IS 10500; WMO/UNEP ozone assessment
Which mercury species is most toxic and bioaccumulative, causing Minamata disease?
C. Methylmercury
Methylmercury biomagnifies in fish and caused Minamata disease in Japan in the 1950s.
Further reading: See the manual sources: Sawyer, McCarty & Parkin; Manahan; Stumm & Morgan; Seinfeld & Pandis; IS 10500; WMO/UNEP ozone assessment
Which parameter measures the oxygen required to chemically oxidise organic matter using potassium dichromate?
A. Chemical oxygen demand (COD)
COD uses dichromate in acid; BOD is microbial oxygen use over 5 days; DO is dissolved oxygen; TOC measures carbon.
Further reading: See the manual sources: Sawyer, McCarty & Parkin; Manahan; Stumm & Morgan; Seinfeld & Pandis; IS 10500; WMO/UNEP ozone assessment
Which international agreement controls the production of ozone-depleting substances such as CFCs?
C. The Montreal Protocol (1987)
Montreal regulates ODS; Kyoto greenhouse gases; Stockholm POPs; Basel hazardous waste trade.
Further reading: See the manual sources: Sawyer, McCarty & Parkin; Manahan; Stumm & Morgan; Seinfeld & Pandis; IS 10500; WMO/UNEP ozone assessment
Which type of radiation is stopped by a sheet of paper but is most hazardous when inhaled or ingested?
A. Alpha particles
Alpha particles have low penetration but high ionisation; inside the body they damage tissue intensely.
Further reading: See the manual sources: Sawyer, McCarty & Parkin; Manahan; Stumm & Morgan; Seinfeld & Pandis; IS 10500; WMO/UNEP ozone assessment
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