# Chemical Thermodynamics

### (ΔH – ΔU) for the formation of carbon monoxide (CO)

(ΔH – ΔU) for the formation of carbon monoxide (CO) from its elements at 298 K is (R = 8.314 JK–1 mol–1)

1. 1238.78 J/mol
2. 2477.57 J/mol
3. –2477.57 J/mol
4. –1238.78 J/mol

### In conversion of limestone to lime

In conversion of limestone to lime,

CaCO3(s) → CaO(s) + CO2(g)

The values of ΔH° and ΔS° are +179.1 kJ/mol and 160.2 J/K respectively at 298 K and 1 bar. Assuming that ΔH° and ΔS° do not change with temperature, temperature above which conversion of limestone to lime will be spontaneous is

1. 1200 K
2. 1118 K
3. 1008 K
4. 845 K

### Standard entropy of X2, Y2 and XY3 are 60, 40 and 50

Standard entropy of X2, Y2 and XY3 are 60, 40 and 50 J K–1 mol–1, respectively. For the reaction, 1/2 X2 + 3/2 Y2 → XY3, ΔH = –30 kJ, to be at equilibrium, the temperature will be

1. 500 K
2. 750 K
3. 1000 K
4. 1250 K

### The heat required to raise the temperature of 1 mole substance by 1°C

The heat required to raise the temperature of 1 mole substance by 1°C is called

1. Thermal capacity
2. Molar heat capacity
3. Specific heat
4. None of these

### The enthalpy change for a reaction does not depend upon the

The enthalpy change for a reaction does not depend upon the

1. use of different reactants for the same product.
2. nature of intermediate reaction steps.
3. physical states of reactants and products.
4. difference in initial or final temperatures of involved substances.

### The heat of atomization of methane and ethane are 360 kJ/mol and 620 kJ/mol, respectively

The heat of atomization of methane and ethane are 360 kJ/mol and 620 kJ/mol, respectively. The longest wavelength of light capable of breaking the C - C bond is (Avogadro number = 6.02×1023, h = 6.62×10-34 J s):

1. 1.49×103 nm
2. 2.48×103 nm
3. 2.48×104 nm
4. 1.49×104 nm

### The heats of combustion of carbon and carbon monoxide are –393.5 and –283.5

The heats of combustion of carbon and carbon monoxide are –393.5 and –283.5 kJ mol–1, respectively. The heat of formation (in kJ) of carbon monoxide per mole is:

1. 676.5
2. –676.5
3. –110.5
4. 110.5