JEE MAIN - Chemistry (2006 - No. 4)
($$\Delta H - \Delta U$$) for the formation of carbon monoxide (CO) from its elements at 298 K is : (R = 8.314 J K–1 mol–1)
–1238.78 J mol–1
1238.78 J mol–1
–2477.57 J mol–1
2477.57 J mol–1
Explanation
For the reaction, $${C_{\left( s \right)}} + {1 \over 2}{O_{2\left( g \right)}} \to CO$$
$$\Delta H = \Delta U + \Delta nRT$$
or $$\,\,\,\,\,\Delta H - \Delta U = \Delta nRT$$
$$\Delta n = 1 - {1 \over 2} = {1 \over 2};\,\,$$
$$\Delta H - \Delta U = {1 \over 2} \times 8.314 \times 298$$
$$ = 1238.78\,Jmo{l^{ - 1}}$$
$$\Delta H = \Delta U + \Delta nRT$$
or $$\,\,\,\,\,\Delta H - \Delta U = \Delta nRT$$
$$\Delta n = 1 - {1 \over 2} = {1 \over 2};\,\,$$
$$\Delta H - \Delta U = {1 \over 2} \times 8.314 \times 298$$
$$ = 1238.78\,Jmo{l^{ - 1}}$$
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