General
✓✗The heat of combustion of benzoic acid (C6H5COOH(s)) measured in a bomb calorimeter at 300 K is −3226.7 kJ mol−1. The enthalpy of combustion (to CO2(g) and H2O(l)) at constant pressure is about (R = 8.314 J K−1 mol−1)
- −3226.7 kJ mol−1
- −3230.4 kJ mol−1
- −3225.5 kJ mol−1
- −3228.0 kJ mol−1
General
✓✗Two moles of an ideal gas expand reversibly and isothermally at 300 K from 10 L to 100 L. The work done is (R = 8.314 J K−1 mol−1)
- −4.99 kJ
- −11.49 kJ
- +11.49 kJ
- −1.15 kJ
General
✓✗According to the third law of thermodynamics, the entropy of a perfectly crystalline substance approaches zero as
- the volume approaches zero
- the pressure approaches zero
- the temperature approaches 0 K
- the temperature approaches 273 K
General
✓✗If ΔfH° of H2O(l) is −286 kJ mol−1, the enthalpy change for 2H2O(l) → 2H2(g) + O2(g) is
- −286 kJ
- +572 kJ
- −572 kJ
- +286 kJ
General
✓✗Consider the liquid−vapour equilibrium: Liquid ⇌ Vapour. Which of the following relations is correct?
- \( \dfrac{d\ln P}{dT} = \dfrac{-\Delta H_v}{RT} \)
- \( \dfrac{d\ln G}{dT^2} = \dfrac{\Delta H_v}{RT^2} \)
- \( \dfrac{d\ln P}{dT^2} = \dfrac{-\Delta H_v}{T^2} \)
- \( \dfrac{d\ln P}{dT} = \dfrac{\Delta H_v}{RT^2} \)
General
✓✗A process in which the temperature of the system remains constant throughout is called
- adiabatic
- isothermal
- isobaric
- isochoric
General
✓✗The heat absorbed at constant pressure is equal to
- the change in Gibbs energy
- the change in enthalpy
- the change in internal energy
- the change in entropy
General
✓✗For an irreversible (spontaneous) process in an isolated system,
- ΔS = 0
- ΔS can have any sign
- ΔS > 0
- ΔS < 0
General
✓✗The enthalpies of formation of C2H4(g), CO2(g) and H2O(l) at 25°C and 1 atm pressure are 52, −394 and −286 kJ mol−1 respectively. The enthalpy of combustion of C2H4(g) will be
- −1412 kJ mol−1
- +1412 kJ mol−1
- −141.2 kJ mol−1
- +141.2 kJ mol−1
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
✓✗A gas is allowed to expand in a well-insulated container against a constant external pressure of 2.5 atm from an initial volume of 2.50 L to a final volume of 4.50 L. The change in internal energy ΔU of the gas, in joules, will be closest to
- −505 J
- +505 J
- −500 J
- 1136.25 J
General
✓✗The heat capacity of a substance at constant pressure (Cp) is defined as
- \( \left(\dfrac{\partial H}{\partial T}\right)_p \)
- \( \left(\dfrac{\partial H}{\partial p}\right)_T \)
- \( \left(\dfrac{\partial U}{\partial T}\right)_p \)
- \( \left(\dfrac{\partial S}{\partial T}\right)_V \)
General
✓✗Assertion: The enthalpy of formation of H2O(l) is more negative than that of H2O(g).
Reason: Heat is released when water vapour condenses to liquid water.
Reason: Heat is released when water vapour condenses to liquid water.
- Both Assertion and Reason are true and Reason is the correct explanation of Assertion
- Both Assertion and Reason are true but Reason is not the correct explanation of Assertion
- Assertion is true but Reason is false
- Both Assertion and Reason are false
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
✓✗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