According to the third law of thermodynamics which one of the following quantities for a perfectly crystalline solid is zero at absolute zero ?
Free energy
Entropy
Enthalpy
Internal energy
The values of ΔH and ΔS for the reaction, C(graphite) + CO2 (g) → 2CO (g) are 170 kJ and 170 JK-1, respectively. This reaction will be spontaneous at
710 K
910 K
1110 K
510 K
The enthalpy and entropy change for the reaction
Br2 (l) + CI2 (g) → 2BrCI (g)
are 30 kJ mol-1 and 105 JK mol-1 respectively. The temperature at which the reaction will be in equilibrium is
285.7 K
273 K
450 K
300 K
Change in enthalpy for reaction
2H2O2(l) → 2H2O(l) + O2 (g)
if heat of formation of H2O2(l) and H2O(l) are -188 and -286 kJ/mol respectively is,
-196 kJ/mol
+ 196 kJ/mol
+ 948 kJ/mol
-948 kJ/mol
For the reaction,
C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(l) at constant temperature, H - E is
+ 3RT
- RT
+ RT
- 3RT
The densities of graphite and diamond at 298 K are 2.25 and 3.31 g cm-3 , respectively. If the standard free energy difference (ΔGo ) is equal to 1895 J mol-1, the pressure at which graphite will be transformed into diamond at 298 K is
9.92 × 106 Pa
9.92 × 105 Pa
9.92 × 108 Pa
9.92 × 107 Pa
A reaction occurs spontaneously if
TS < H and both H and S are + ve
TS > H and both H and S are + ve
TS = H and both H and S are + ve
TS > H and H and is +ve and S is -ve
Standard Gibb's free energy change for the isomerisation reaction
cis-2-pentene trans-2-pentene is -3.67 kJ/mol at 400 K. If more trans-2-pentene is added to the reaction vessel, then
more cis-2-pentene is formed
equilibrium remains unaffected
additional trans-2-pentene is formed
equilibrium is shifted in forward direction
Identify the correct statement regarding entropy.
At absolute zero temperature, entropy of a perfectly crystalline substance is taken to be zero
At absolute zero temperature, the entropy of a perfectly crystalline substance is +ve
At absolute zero temperature, the entropy of all crystalline substances is to be zero
At 0o C, the entropy of a perfectly crystalline substance is taken to be zero
For the gas phase reaction,
PCI5 (g) PCI3(g) + CI2(g)
Which of the following conditions are correct ?
ΔH = 0 and ΔS < 0
ΔH > 0 and ΔS > 0
ΔH < 0 and ΔS < 0
ΔH > 0 and ΔS < 0
