| \[{{H}_{2}}\left( g \right)\,\,+\,\,{{F}_{2}}\left( g \right)\,\,\,\to \,\,2HF\left( g \right)\text{ }\Delta H\,\,=\,\,-537\text{ }kJ\] \[C\left( s \right)\,\,+\,\,2{{F}_{2}}\left( g \right)\,\,\to \,\,C{{F}_{4}}\left( g \right)\text{ }\Delta H\,\,=\,\,-680\text{ }kJ\] \[2C\left( s \right)\,\,+\,\,2{{H}_{2}}\left( g \right)\,\,\to \,\,{{C}_{2}}{{H}_{4}}\left( g \right)\text{ }\Delta H\,\,=\,\,52\text{ }kJ\] |
A) -1165 kJ
B) -2486 kJ
C) +1165 kJ
D) +2486 kJ
Correct Answer: B
Solution :
\[-Eq\left( 3 \right)\,\,+\,\,2x\text{ }eq\left( 2 \right)\,\,+\,\,2x\text{ }eq\left( 1 \right)=Desired\text{ }equation\]\[-\Delta {{H}_{3}}\,\,+\,\,2x\,\Delta {{H}_{2}}\,\,+\,\,2x\,\Delta {{H}_{1}}\,\,=\,\,\Delta H\] \[-52+\left( 2x-680 \right)+\left( 2x-537 \right)=\Delta H\] \[-52-1360-1074=-2486=\Delta H\]
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