121.

In an isothermal process

• q = 0 and $∆$E = 0

• q ≠ 0 and $∆$E = 0

• q = 0 and $∆$E ≠ 0

• q ≠ 0 and $∆$E ≠ 0

Minimum work is obtained when 1 kg of...gas expanded under 500 kPa to 200 kPa pressure at 0°C

• chlorine

• oxygen

• nitrogen

• methane

Which one of the following represents the graph between log p (on Y-axis) and 1/T  on X-axis)? (p = vapour pressure of a liquid, T = absolute temperature).

When 10 g of methane is completely burnt in oxygen, the heat evolved is 560 kJ. What is the heat of combustion (in kJ mol^-1) of methane?

• -1120

• -968

• -896

• -560

Calculate the heat of combustion (in kJ) of methane from the following data :

(i) C_(graphite) + 2H₂ (g) → CH₄ (g) ; $∆$H = -74.8 kJ

(ii) C_(graphite) + O₂ (g) → CO₂ (g) ; $∆$H = -393.5 kJ

(iii) H₂ (g) + 1/2 O₂ (g) → H₂O (l) ; $∆$H = -286.2 kJ

• -891.1

• -816.3

• -965.9

• -1040.7

Which of the following is an endothermic reaction?

• N₂ (g) + 3H₂ (g) - 92 kJ → 2NH₃ (g)

• N₂ (g) + O₂ (g) + 180.8 kJ → 2NO (g)

• H₂ (g) + Cl₂ (g) → 2HCl (g) + 184.6 kJ

• C (graphite) + 2H₂ (g) → CH₂ (g) + 74.8 kJ

Which of the following is not correct?

• 3O₂ $\underset{\mathrm{discharge}}{\overset{\mathrm{silent} \mathrm{electric}}{\rightleftarrows }}$ 2O₃ ; $∆$H = -284.5 kJ

• Ozone undergoes addition reaction with unsaturated carbon compounds

• Sodium thuosulphate reacts with I₂ to form sodium tetrathionate and sodium iodide.

• Ozone oxidises lead sulphide to lead sulphate.

Which of the following is not correct?

• Dissolution of NH₄Cl in excess of water is an endothermic process.

• Neutralisation process is always exothermic

• The absolute value of enthalpy (H) can be determined experimentally.

• The heat of reaction at constant volume is denoted by ΔE.

Identify the reaction for which $∆\mathrm{H} \ne ∆\mathrm{E}$ :

• S(rhombic) + O₂ (g) → SO₂ (g)

• N₂ (g) + O₂ (g) → 2NO (g)

• H₂ (g) + Cl₂ (g) → 2HCl (g)

• CO (g) + $\frac{1}{2}$O₂ (g) → CO₂ (g)

Calculate $∆$H in kJ for the following reaction:

C (g) + O₂ (g) → CO₂ (g)

Given that, 

H₂O (g) + C (g) → CO (g) + H₂ (g) ; $∆$H = +131 kJ

CO (g) + $\frac{1}{2}$O₂ (g) → CO₂ (g); $∆$H = -282 kJ

H₂ (g) + $\frac{1}{2}$O₂ (g) → H₂O (g); $∆$H = -242 kJ

• -393

• +393

• +655

• -655