General
✓✗For a sample of a perfect gas, when its pressure is changed isothermally from pi to pf, the entropy change is given by
- \( \Delta S = nR\ln\dfrac{p_f}{p_i} \)
- \( \Delta S = nR\ln\dfrac{p_i}{p_f} \)
- \( \Delta S = nRT\ln\dfrac{p_f}{p_i} \)
- \( \Delta S = RT\ln\dfrac{p_i}{p_f} \)
General
✓✗The ΔG of a process is the maximum
- heat that can be absorbed
- non-expansion (useful) work that can be obtained at constant T and p
- expansion work only
- entropy change
General
✓✗At 298 K, the equilibrium constant of a reaction is 1.0 × 10−4. If ΔH° = +40 kJ, then ΔS° is about (2.303RT = 5.71 kJ mol−1)
- +57.6 J K−1
- −57.6 J K−1
- +211 J K−1
- +134.2 J K−1
General
✓✗Given A → B, ΔH = +x and B → C, ΔH = +y. The enthalpy change for C → A is
- x − y
- y − x
- −(x + y)
- x + y
General
✓✗For the reaction N2(g) + 3H2(g) → 2NH3(g), ΔH = −92.4 kJ at 298 K. The value of ΔU is (R = 8.314 J K−1 mol−1)
- −92.4 kJ
- −97.4 kJ
- −89.9 kJ
- −87.4 kJ
General
✓✗At constant temperature and pressure, a process is spontaneous if
- ΔH > 0
- ΔG = 0
- ΔG > 0
- ΔG < 0
General
✓✗The heat required to raise the temperature of 50 g of water from 20 °C to 30 °C is (specific heat of water = 4.18 J g−1 K−1)
- 209 J
- 4180 J
- 2090 J
- 20.9 J
General
✓✗5 litres of an ideal gas at 10 atmosphere pressure expands isothermally into a vacuum until its volume is 15 litres. Which of the following is the correct statement about the work done in the expansion and the heat absorbed or released?
- The work done is zero and the heat is also zero.
- The work done is greater than zero and the heat is zero.
- Both the heat and the work done are greater than zero.
- The heat absorbed is less than zero and the work done is positive.
General
✓✗The first law of thermodynamics is a statement of the law of
- constant proportions
- increase of entropy
- conservation of energy
- conservation of mass
General
✓✗The decomposition CaCO3(s) → CaO(s) + CO2(g) has ΔH° = +178 kJ and ΔS° = +160 J K−1. The temperature above which it becomes spontaneous is about
- 298 K
- 178 K
- 1112 K
- 1.11 K
General
✓✗Given: enthalpy of sublimation of C(graphite) = 717 kJ mol−1, bond enthalpy of H−H = 436 kJ mol−1, ΔfH of CH4(g) = −75 kJ mol−1. The average C−H bond enthalpy is about
- 358 kJ mol−1
- 416 kJ mol−1
- 270 kJ mol−1
- 1664 kJ mol−1
General
✓✗The standard Gibbs energy of formation of an element in its standard state is
- equal to its enthalpy of atomisation
- positive
- negative
- zero
General
✓✗One mole of an ideal gas expands reversibly and isothermally at 27 °C so that its pressure falls from 10 atm to 1 atm. The heat absorbed is (R = 2 cal K−1 mol−1)
- 0
- 1381.8 cal
- −1381.8 cal
- 600 cal
General
✓✗Statement I: Work done in the reversible isothermal expansion of an ideal gas is greater than that in an irreversible isothermal expansion between the same two states.
Statement II: In a free expansion of an ideal gas, the work done is zero.
Statement II: In a free expansion of an ideal gas, the work done is zero.
- 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
✓✗The following two reactions are known:
Fe2O3(s) + 3CO(g) → 2Fe(s) + 3CO2(g); ΔH = −26.8 kJ
FeO(s) + CO(g) → Fe(s) + CO2(g); ΔH = −16.5 kJ
The value of ΔH for the reaction Fe2O3(s) + CO(g) → 2FeO(s) + CO2(g) is
Fe2O3(s) + 3CO(g) → 2Fe(s) + 3CO2(g); ΔH = −26.8 kJ
FeO(s) + CO(g) → Fe(s) + CO2(g); ΔH = −16.5 kJ
The value of ΔH for the reaction Fe2O3(s) + CO(g) → 2FeO(s) + CO2(g) is
- −10.3 kJ
- +6.2 kJ
- −43.3 kJ
- +10.3 kJ