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(A) The standard heats of formation of a...

(A) The standard heats of formation of at 298 K for `CCI_(4)(g), H_(2)O(g), CO_(2)(g) and HCI(g)` are `-25.5, -57.8, -94.1, and -22.1`` kcal mol^(-1)` respectively. Calculate `Delta_(r)H^(oplus)` for the reaction
`CCI_(4)(g) + 2H_(2)O(g) rightarrow CO_(2)(g) + 4 HCI (g)`
Hint : `Delta_(r)H^(oplus) = SigmaDelat_(f)H_("ssReactants")^(oplus)`
(B) Why `DeltaH_(f)^(@)` of elements is zero?

Text Solution

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`Delta H = -94.1 + 4 xx (-22.1)-[-25.5 + 2xx 57.8] = -94.1 -88.4 + 25.5 + 115 .6 = -41.4 kcal`.
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