General
✓✗For a reaction, ΔH = +30 kJ and ΔS = +75 J K−1. The minimum temperature above which it becomes spontaneous is
- 300 K
- 225 K
- 2.5 K
- 400 K
General
✓✗For the isothermal expansion of an ideal gas, ΔU is
- negative
- positive
- zero
- equal to qp
General
✓✗At 298 K, K for a reaction is 1.0 × 105. The value of ΔG° is about (2.303RT = 5.71 kJ mol−1)
- +28.6 kJ mol−1
- −28.6 kJ mol−1
- −5.71 kJ mol−1
- −11.4 kJ mol−1
General
✓✗An ideal gas expands from 2 L to 6 L in two steps at constant temperature: first against a constant external pressure of 3 atm up to 4 L, then against 2 atm up to 6 L. The total work done by the gas is (1 L atm = 101.3 J)
- 405 J
- 810 J
- 1013 J
- 1216 J
General
✓✗Adsorption of a gas on a solid surface is a spontaneous process in which the gas molecules lose much of their freedom of movement. Which of the following statements is correct for this process?
- ΔS is positive and, therefore, ΔH should also be highly positive
- ΔS is positive and, therefore, ΔH should be negative
- ΔS is negative and, therefore, ΔH should be highly negative
- ΔS is negative and, therefore, ΔH should be highly positive
General
✓✗For a reaction at 300 K, ΔSsystem = −50 J K−1 and ΔH = −30 kJ. The total entropy change of the universe is
- −150 J K−1
- +50 J K−1
- −50 J K−1
- +150 J K−1
General
✓✗Given: 2Fe(s) + 3/2 O2(g) → Fe2O3(s), ΔH = −824 kJ; 2Al(s) + 3/2 O2(g) → Al2O3(s), ΔH = −1676 kJ. The enthalpy change of the thermite reaction 2Al(s) + Fe2O3(s) → 2Fe(s) + Al2O3(s) is
- −426 kJ
- +852 kJ
- −2500 kJ
- −852 kJ
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 ratio of two extensive properties is
- an extensive property
- always dimensionless
- an intensive property
- a path function
General
✓✗If ΔG° for a reaction is −2.303RT, then K equals
- 0.1
- 10
- e
- 1
General
✓✗Which of the following statements about entropy is correct?
- Entropy is an intensive property.
- The entropy of a pure crystalline solid is zero at 298 K.
- The entropy of the system must increase in every spontaneous process.
- The entropy of the universe always increases in a spontaneous process.
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
✓✗In a constant-volume (bomb) calorimeter, the heat measured is used to obtain ΔH using the relation
- ΔH = ΔU − TΔS
- ΔH = ΔU/ΔngRT
- ΔH = ΔU + CVΔT
- ΔH = ΔU + ΔngRT
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
✓✗Arrange in increasing order of standard molar entropy: H2O(l), H2O(s) (ice), H2O(g)
- H2O(l) < ice < H2O(g)
- H2O(g) < H2O(l) < ice
- ice < H2O(g) < H2O(l)
- ice < H2O(l) < H2O(g)