QJEEM21Ch836b: JEE Main 2021 Chemistry - Class 11 JEEM21Ch836b Solution: The reaction of cyanamide, NH 2 CN (s) with oxygen was run in a …

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The reaction of cyanamide, NH₂CN_(s) with oxygen was run in a bomb calorimeter and

Δ

U was found to be

-

742.24 kJ mol^{$-$ 1}. The magnitude of

Δ

H₂₉₈ for the reaction

N H_{2} C H_{(S)} + \frac{3}{2} O_{2 (g)} \to N_{2 (g)} + O_{2 (g)} + H_{2} O_{(I)}

is _________ kJ. (Rounded off to the nearest integer) [Assume ideal gases and R = 8.314 J mol^{$-$ 1} K^{$-$ 1}]

Accepted Answer

N H_{2} C N (s) + \frac{3}{2} O_{2} (g) \overset{}{⟶} N_{2} (g) + C O_{2} (g) + H_{2} O (l)

Δ n g = (1 + 1) - \frac{3}{2} = \frac{1}{2}

Δ H = Δ U + Δ n g R T

= - 742.24 + \frac{1}{2} \times \frac{8.314 \times 298}{1000}

= - 742.24 + 1.24

= - 741

kJ/mol

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