A) 43.8 kJ
B) \[-43.8\text{ }kJ\]
C) \[-68kJ\]
D) 68kJ
Correct Answer: A
Solution :
Given \[{{H}^{+}}+O{{H}^{-}}\to {{H}_{2}}O;\] \[\Delta H=-55.9kJ\] ...(i) \[HCN+O{{H}^{-}}\to {{H}_{2}}O+C{{N}^{-}}\] \[\Delta H=-121kJ\] ...(ii) on reversing (i) we get \[{{H}_{2}}O\xrightarrow[{}]{{}}{{H}^{+}}+O{{H}^{-}}\] \[\Delta H=+55.9\text{ }kJ\] ...(iii) on adding (iii) to (ii) we get \[HCN\xrightarrow[{}]{{}}{{H}^{+}}+C{{N}^{-}}\] \[\Delta H=+43.8\text{ }kJ\]
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