Given that bond energies of H—H and CI—CI are 430 kJ mol-1 and 240 kJ mol-1. respectively and ΔHf for HCI is
-90 kJ mol-1. Bond enthalpy of HCI is
290 kJ mol-1
380 kJ mol-1
425 kJ mol-1
245 kJ mol-1
Identify the correct statement for change of Gibb's energy for a system (ΔGsystem ) at constant temperature and pressure.
If ΔGsystem > 0, the process is spontaneous
If ΔGsystem = 0, the system has attained equilibrium
If ΔGsystem = 0, the system is still moving in a particular direction
If ΔGsystem< 0, the process is not spontaneous
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
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
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
Bond dissociation enthalpy of H2,CI2 and HCI are 434, 242 and 431 kJ mol-1 respectively. Enthalpy of formation of HCI is
93 kJ mol-1
-245 kJ mol-1
-93 kJ mol-1
The enthalpy of combustion of H2, cyclohexene (C6H10) and cyclohexane (C6H12) are - 241, -3800 and -3920 kJ per mol respectively. Heat of hydrogenation of cyclohexene is
- 121 kJ per mol
+ 121 kJ per mol
+ 242 kJ per mol
- 242 kJ per mol
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
A chemical reaction will be spontaneous if it is accompanied by a decrease in
entropy of the system
enthalpy of the system
internal energy of the system
free energy of the system
Which of the following pairs of a chemical reaction is certain to result in a spontaneous reaction ?
Exothermic and decreasing disorder
Endothermic and increasing disorder
Exothermic and increasing disorder
Endothermic and decreasing disorder
