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# The reaction of cyanamide, NH2CN (s), with dioxygen was carried out in a bomb calorimeter, and Delta U was found to be minus 742.7 kJ mol raised to minus 1 at 298 K. Calculate enthalpy change for the reaction at 298 K.

6.8  The reaction of cyanamide,$NH_2 CN$ (s), with dioxygen was carried out in a bomb calorimeter, and $\Delta U$ was found to be $-742.7 KJ mol ^{-1}$ at 298 K. Calculate enthalpy change for the reaction at 298 K.

$NH_2 CN ( g ) + \frac{3}{2} O_2 (g) \rightarrow N_2 + CO_2 ( g ) H_2 O ( l)$

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Given information,
$\Delta U = -742.7kJmol^{-1}$
T = 298 K
R = 8.314$\times 10^{-3}$

$\Delta n_g =$$n_g$(products)$- n_g$(reactants)
= (2 - 1.5)
= 0.5 moles

The enthalpy change for the reaction is expressed as;

$\Delta H = \Delta U+n_gRT$
where, $\Delta U$ = change in internal energy  and
$\Delta n_g =$ change in no. of moles

By putting the values we get,
$\Delta H = (-742.7)+0.5(298)(8.314\times 10^{-3})$
$=-741.5 kJmol^{-1}$

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