The standard molar heats of formation of ethane, carbon dioxide, and liquid water are `-21.1, -94.1`, and `-68.3kcal`, respectively. Calculate the standard molar heat of combustion of ethane.

Options

A. `-372` Kcal
B. `-162` Kcal
C. `-240` Kcal
D. `-183.5` Kcal

Answer

A

Explanation

`C_(2)H_(6(g))+(7)/(2)O_(2(g))rarr 2CO_(2(g))+3H_(2)O_((l)) , Delta H_("comb.") = ?`
`Delta H = Sigma (Delta E_(f))_(P)-Sigma(Selta E_(f))_(R )`
`Delta H=[2xx(-94.1)+3xx(-68.3)]-[1xx(-21.1)+0]`
`Delta H_("Comb.")=-372 Kcal`