The heats of formation of `CO_(2(g)) and H_(2)O_((l))` are `- 398 and -285 kJ mol^(-1)` respectively. The heat of combustton of methane is -390 kJ. The heat of formation of methane will be

Options

A. -550 kJ
B. - 500 kJ
C. -578 kJ
D. -600 kJ

Answer

C

Explanation

`C_((s))+2H_(2(g))rarr CH_(4(g))" "Delta H=?`
`C_((s))+O_(2(g))rarr CO_(2(g))" "Delta H_(1)=-398 kJ`
`2H_(2(g))+O_(2(g)) rarr 2H_(2)O_((l))" "Delta H_(2)=-570 kJ`
`CO_(2)+2H_(2)O rarr CH_(4(g))+2O_(2(g))" "Delta H_(3) =+390 kJ`
`Delta H=-578 kJ`