Question

The reaction of cyanamide NH₂CN (s) with oxygen was carried out in a bomb

caloriemeter and Dq_v at 300 K was measured to be – 750 kJ/mol. The value of DH per mole of NH₂CN (s) in the given reaction is-

• A. – 741.75 kJ/mol
• B. – 748.75 kJ/mol
• C. – 752.75 kJ/mol
• D. –750 kJ/mol

Answer 1

Answer: (B)

– 748.75 kJ/mol

Answer 2

The combustion reaction is :

NH₂CN (s) + $\frac{3}{2}$O₂ (g) ¾®

N₂ (g) + CO₂ (g) + H₂O (l)

Dn = $\frac{1}{2}$

DH = DE + Dn RT = –750 +$\frac{1}{2}$ × 8.314 × 10^–3 × 300

or DH = – 750 + 0.15 × 8.314 = – 748.75 kJ/mol