Heat of combustion $∆\mathrm{H}°$ for C(s), H₂(g) and CH₄(g) are -94, -68 and -213 kcal/mol. Then, $∆\mathrm{H}°$ for 

C(s) + 2H₂(g) $\to$CH₄(g) is                                                                 

1. -17 kcal/mol                         

2. -111 kcal/mol

3. -170 kcal/mol                       

4. -85 kcal/mol

If $∆{\mathrm{H}}_{\mathrm{f}}^{°}$(C₂H₄) and $∆{\mathrm{H}}_{\mathrm{f}}^{°}$(C₂H₆) are x₁ and x₂ kcal/mol then heat of hydrogenation of C₂H₄ is :-

(1) x₁ + x₂

(2) x₁ - x₂

(3) x₂ - x₁

(4) x₁ + 2x₂

One mole of methanol when burnt in O₂ gives out 723 kJ mol^-1 of heat. If one mole of O₂ is used, what will be the amount of heat evolved?

1. 482 kJ
2. 241 kJ
3. 723 kJ               
4. 924 kJ

The heat of combustion of carbon to CO₂ is -393.5 kJ/mol. The heat released upon the

formation of 35.2 g of CO₂ from carbon and oxygen gas is

1. -315 kJ               

2. +315 kJ             

3. -630 kJ                 

4. -3.15 kJ

Enthalpy change for the reaction,

 4H(g) $\to$2H₂(g) is -869.6 kJ

The dissociation energy of H-H bond is

1. -869.6 kJ                 

2. + 434.8 kJ

3. +217.4 kJ                 

4. -434.8 kJ