The heat of combustion of carbon to CO₂ is -393.5 KJ/mol. The heat changed 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. +630 KJ

Consider the following reactions: 

Enthalpy of formation of H₂O(l) is :

1. $-x_3$ $kJ$ $mo{l}^{-1}$

2. $-x_4$ $kJ$ $mo{l}^{-1}$

3. $-x_1$ $kJ$ $mo{l}^{-1}$

4. $-x_2$ $kJ$ $mo{l}^{-1}$

Given, the following reaction:

$N_2{H}_4\left(g\right)\underset{ }{\to }{N}_2{H}_2\left(g\right)+H_2\left(g\right);$
Given:  ∆ H^∘ = 109 kJ/mol

B.E. of (N-N) = 163 kJ/mol

B.E. of (N-H) = 391 kJ/mol

B.E. of (H-H) = 436 kJ/mol

Calculate the bond enthalpy of N = N.

1. 182 kJ/mol

2. 400 kJ/mol

3. 300 kJ/mol

4. 218 kJ/mol