JEE MAIN - Chemistry (2004 - No. 2)
The enthalpies of combustion of carbon and carbon monoxide are -393.5 and -283 kJ mol-1
respectively. The enthalpy of formation of carbon monoxide per mole is :
110.5 kJ
-110.5 kJ
-676.5 kJ
676.5 kJ
Explanation
$$\left( i \right)\,\,\,C + {O_2}\rightleftharpoons C{O_2},$$
$$\,\,\Delta H = - 393.5\,kJmo{l^{ - 1}}$$
$$\left( {ii} \right)\,\,\,CO + {1 \over 2}{O_2}\rightleftharpoons\,C{O_2},$$
$$\,\,\,\,\,\,\,\,\Delta H = - 283.0\,kJmo{l^{ - 1}}$$
Operating $$(i)-(ii),$$ we have
$$C + {1 \over 2}{O_2} \to CO$$
$$\,\,\,\,\,\,\,\,\Delta H = - 110.5\,kJmo{l^{ - 1}}$$
$$\,\,\Delta H = - 393.5\,kJmo{l^{ - 1}}$$
$$\left( {ii} \right)\,\,\,CO + {1 \over 2}{O_2}\rightleftharpoons\,C{O_2},$$
$$\,\,\,\,\,\,\,\,\Delta H = - 283.0\,kJmo{l^{ - 1}}$$
Operating $$(i)-(ii),$$ we have
$$C + {1 \over 2}{O_2} \to CO$$
$$\,\,\,\,\,\,\,\,\Delta H = - 110.5\,kJmo{l^{ - 1}}$$
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