(1) For the given heat of reaction,
(i) `C(s)+O_(2)(g)=CO_(2)(g)+97 kcal`
(ii) `CO_(2)(g)+C(s)=2CO(g)-39 kcal`
the heat of combustion of `CO(g)` is:

Options

A. 68 kcal
B. `-68` kcal
C. `+48` kcal
D. none of these

Answer

A

Explanation

Substracting equation (ii) from equation (i), we get,
`C(s) + O_(2)(g) = CO_(2)(g) + 97 kcal`………….(i)
`CO_(2)(g) + C(s) = 2CO(g) - 39 kcal`……………(ii)
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`-CO_(2)(g) + O_(2)(g) =CO_(2)(g) -2CO(g) + 136 kcal`
`rArr 2CO(g) + O_(2)(g) =2CO_(2)(g) + 136 kcal`
`rArr CO(g)+1/2O_(2)(g) = CO_(2)(g) + 68 kcal`
Required value = 68 kcal
Hence (A) is the correct answer.