A) \[-1802kJ\]
B) \[+1802kJ\]
C) \[+237kJ\]
D) \[-800kJ\]
Correct Answer: C
Solution :
\[2C(s)+2{{O}_{2}}(g)\xrightarrow{{}}2C{{O}_{2}}(g);\] \[\Delta H=-787kJ\] ??(i) \[{{H}_{2}}(g)+\frac{1}{2}{{O}_{2}}(g)\xrightarrow{{}}{{H}_{2}}O(l);\] \[\Delta H=-286kJ\] ??.(ii) \[{{C}_{2}}{{H}_{2}}(g)+2\frac{1}{2}{{O}_{2}}(g)\xrightarrow{{}}2C{{O}_{2}}(g)+{{H}_{2}}O(l);\] \[\Delta H=-1310kJ\] ??.(iii) Add the Eqs. (i) and (ii) and subtract Eq. (iii) from them., \[2C+{{H}_{2}}\xrightarrow{{}}{{C}_{2}}{{H}_{2}}-787-286+1310\] \[2C+{{H}_{2}}\xrightarrow{{}}{{C}_{2}}{{H}_{2}}-1073+1310\] \[2C+{{H}_{2}}\xrightarrow{{}}{{C}_{2}}{{H}_{2}}+237\] Hence, the heat of formation of acetylene is \[+237kJ\].
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