The average S–F bond energy in kJ mol^–1 of SF₆ is:

 [The values of standard enthalpy of formation of
SF₆(g), S(g), and F(g) are –1100, 275, and 80 kJmol^–1 respectively.]

Lattice energy and enthalpy of the solution of NaCl are 788 kJ mol^–1 and 4 kJ mol^–1 , respectively. The hydration enthalpy of NaCl is:
1. –780 kJ mol^–1
2. –784 kJ mol^–1
3. 780 kJ mol^–1
4.  784 kJ mol^–1

The standard enthalpy of formation of NH₃ is –46 0. kJ mol⁻¹. If the enthalpy of formation of H₂ from its atoms is –436 kJ mol⁻¹ and that of N₂ is –712 kJ mol⁻¹, the average bond enthalpy of N − H bond in NH₃ is:

1. $-1102\mathrm{kJ}{\mathrm{mol}}^{-1}$

2. $-964\mathrm{kJ}{\mathrm{mol}}^{-1}$

3. $+352\mathrm{kJ}{\mathrm{mol}}^{-1}$

4. $+1056\mathrm{kJ}{\mathrm{mol}}^{-1}$

Which of the following is the standard enthalpy of formation of carbon monoxide (CO), if the standard enthalpies of combustion of carbon (C) and carbon monoxide (CO) respectively are −393.5 kJ mol⁻¹  and −283 kJ mol⁻¹?

1. 110.5 kJ

2. 676.5 kJ

3. -676.5 kJ

4. -110.5 kJ

If at 298 K the bond energies of C-H, C-C, C = C and H-H bonds are respectively 414, 347, 615, and 435 kJ mol^–1, the value of enthalpy change for the reaction at 298 K will be:

\(\mathrm{H}_{2} \mathrm{C}=\mathrm{CH}_{2}(g)+\mathrm{H}_{2}(g) \longrightarrow \mathrm{H}_{3} \mathrm{C}-\mathrm{CH}_{3}(g)\)

1. +250 kJ 

2. –250 kJ 

3. +125 kJ 

4. –125 kJ