General
✓✗Enthalpy (H) is defined as
- G + TS − pV
- U − pV
- U + TS
- U + pV
General
✓✗The enthalpy of atomisation of methane, CH4(g) → C(g) + 4H(g), is 1665 kJ mol−1. The average C−H bond enthalpy is about
- 208 kJ mol−1
- 832 kJ mol−1
- 416 kJ mol−1
- 1665 kJ mol−1
General
✓✗Equal masses of water (specific heat 4.18 J g−1 K−1) and of copper (0.385 J g−1 K−1) absorb the same amount of heat. The rise in temperature of copper compared with water is
- about 2 times larger
- about 10.9 times larger
- about 10.9 times smaller
- the same
General
✓✗The enthalpy change and internal energy change for a gaseous reaction are related by ΔH = ΔU + ΔngRT. Here Δng is
- total moles of gaseous species
- moles of all products minus moles of all reactants
- moles of gaseous products minus moles of gaseous reactants
- moles of gaseous reactants minus moles of gaseous products
General
✓✗The bond dissociation energies of X2, Y2 and XY are in the ratio 1 : 0.5 : 1. ΔH for the formation of XY is −200 kJ mol−1. The bond dissociation energy of X2 will be
- 400 kJ mol−1
- 200 kJ mol−1
- 800 kJ mol−1
- 100 kJ mol−1
General
✓✗The standard entropies (J K−1 mol−1) of N2(g), H2(g) and NH3(g) are 191.5, 130.6 and 192.3. For N2(g) + 3H2(g) → 2NH3(g), ΔH° = −92.2 kJ. The value of ΔG° at 298 K is about
- −33.0 kJ
- −151.4 kJ
- +33.0 kJ
- −92.2 kJ
General
✓✗A sample of an ideal gas is taken through two different paths from state 1 to state 2. Along path I, q = +500 J and w = −200 J. Along path II, q = +350 J. The work along path II is
- −50 J
- −150 J
- +50 J
- −350 J
General
✓✗If ΔfusH and ΔvapH of a substance are 6 and 45 kJ mol−1 respectively (at the same temperature), its enthalpy of sublimation is
- 270 kJ mol−1
- 39 kJ mol−1
- 51 kJ mol−1
- 7.5 kJ mol−1
General
✓✗Statement I: The entropy of a system can decrease in a spontaneous process.
Statement II: The entropy of an isolated system can decrease in a spontaneous process.
Statement II: The entropy of an isolated system can decrease in a spontaneous process.
- Both Statement I and Statement II are correct
- Both Statement I and Statement II are incorrect
- Statement I is correct but Statement II is incorrect
- Statement I is incorrect but Statement II is correct
General
✓✗Which of the following processes is accompanied by an increase in entropy?
- Sublimation of dry ice
- Freezing of a liquid
- Condensation of steam
- Crystallisation of salt from solution
General
✓✗For a reaction at 300 K, ΔG° = −11.46 kJ. If Q = 10 at a certain instant, ΔG is about (R = 8.314 J K−1 mol−1)
- +5.72 kJ
- −17.2 kJ
- −11.46 kJ
- −5.72 kJ
General
✓✗The enthalpy change when one mole of a substance dissolves in a specified (large) amount of solvent is called the enthalpy of
- hydration
- formation
- solution
- fusion
General
✓✗If 100 J of heat raises the temperature of 10 g of a metal from 20 °C to 45 °C, the specific heat of the metal is
- 0.4 J g−1 K−1
- 4 J g−1 K−1
- 0.25 J g−1 K−1
- 2.5 J g−1 K−1
General
✓✗100 g of water at 80 °C is mixed with 50 g of water at 20 °C in an insulated vessel of negligible heat capacity. The final temperature is
- 40 °C
- 60 °C
- 55 °C
- 50 °C
General
✓✗The enthalpy of neutralisation of a strong acid by a strong base is nearly constant (−57.3 kJ mol−1) because
- all salts have the same lattice enthalpy
- all acids have the same molar mass
- water has a high heat capacity
- the net reaction is always H+(aq) + OH−(aq) → H2O(l)