CSIR-UGC NET Environmental Chemistry: practice questions

1 · Chemical equilibrium, thermodynamics and reaction kinetics · medium

According to Le Chatelier's principle, raising the temperature of an exothermic equilibrium will

1. shift it towards the reactants
2. have no effect on the equilibrium position
3. shift it towards the products
4. double the equilibrium constant

2 · Chemical equilibrium, thermodynamics and reaction kinetics · medium

If the reaction quotient Q is smaller than the equilibrium constant K, the reaction will

1. proceed in the reverse direction
2. stop permanently
3. proceed in the forward direction
4. already be at equilibrium

3 · The carbonate system and ocean acidification · medium

Which carbonate species dominates dissolved inorganic carbon at pH 8.3 in fresh water at 25 °C (pKa1 6.35, pKa2 10.33)?

1. Bicarbonate, about 98 per cent
2. Dissolved CO2, about 98 per cent
3. Carbonate, about 98 per cent
4. Equal amounts of all three species

4 · Redox reactions, pe-pH diagrams and redox zonation · medium

A redox potential of +0.40 V is measured at 25 °C. What is the corresponding pe (pe = E/0.0592)?

1. -6.8
2. 0.024
3. 6.8
4. 0.40

5 · Redox reactions, pe-pH diagrams and redox zonation · hard

Using the Nernst equation E = E° − (0.0592/n) log Q at 25 °C, what happens to E for a one-electron reduction when Q increases tenfold?

1. E is unchanged
2. E decreases by 0.592 V
3. E decreases by 0.0592 V
4. E increases by 0.0592 V

6 · Composition and structure of the atmosphere · medium

Which radical is called the 'detergent of the atmosphere' because it initiates oxidation of most trace gases?

1. The hydroxyl radical (OH)
2. The nitrate radical (NO3)
3. The superoxide ion (O2⁻)
4. The chlorine atom (Cl)

7 · Composition and structure of the atmosphere · hard

A gas has an atmospheric burden of 5000 Tg and is removed at 500 Tg per year. Assuming steady state, what is its atmospheric lifetime?

1. 0.1 year
2. 5500 years
3. 2500 years
4. 10 years

8 · Stratospheric ozone chemistry and ozone-depleting substances · medium

In a catalytic ozone-destruction cycle, Cl + O3 → ClO + O2 is followed by ClO + O → Cl + O2. What is the net reaction?

1. 2O3 → 3O2 + Cl
2. Cl + O3 → ClO + O2
3. O2 → 2O
4. O + O3 → 2O2

9 · Stratospheric ozone chemistry and ozone-depleting substances · medium

Why does the Antarctic ozone hole form mainly in spring?

1. Ozone is produced only in autumn over Antarctica
2. Spring winds blow ozone towards the equator
3. Volcanic eruptions occur mostly in spring
4. Spring sun frees cloud-activated chlorine