JEE MAIN - Chemistry (2016 (Offline) - No. 9)
The heats of combustion of carbon and carbon monoxide are –393.5 and –283.5 kJ mol–1, respectively. The
heat of formation (in kJ) of carbon monoxide per mole is :
676.5
-676.5
–110
110.5
Explanation
Given
$$C\left( s \right) + {O_2}\left( g \right) \to C{O_2}\left( g \right);$$
$$\Delta H = - 393.5\,\,kJ\,mo{l^{ - 1}}......\left( i \right)$$
$$CO\left( g \right) + {1 \over 2}{O_2}\left( g \right) \to C{O_2}\left( g \right);$$
$$\Delta H = - 283.5\,kJ\,mo{l^{ - 1}}\,\,\,\,\,....\left( {ii} \right)$$
$$\therefore$$ Heat of formation of
$$Co = eqn\left( i \right) - eqn\left( {ii} \right)$$
$$ = - 393.5 - \left( { - 283.5} \right)$$
$$ = - 110\,kJ$$
$$C\left( s \right) + {O_2}\left( g \right) \to C{O_2}\left( g \right);$$
$$\Delta H = - 393.5\,\,kJ\,mo{l^{ - 1}}......\left( i \right)$$
$$CO\left( g \right) + {1 \over 2}{O_2}\left( g \right) \to C{O_2}\left( g \right);$$
$$\Delta H = - 283.5\,kJ\,mo{l^{ - 1}}\,\,\,\,\,....\left( {ii} \right)$$
$$\therefore$$ Heat of formation of
$$Co = eqn\left( i \right) - eqn\left( {ii} \right)$$
$$ = - 393.5 - \left( { - 283.5} \right)$$
$$ = - 110\,kJ$$
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