The heat of combustion of hydrocarbon C_(x)H_(y) is ''a'' calories and heat of formation of CO_(2) and H_(2)O are ''b'' and 'c' calories respectively then the heat of formation of hydrocarbon C_(8)H is (in calories)

The heat of combustion of hydrocarbon C_(x)H_(y) is ''a'' calories and

1.	The heat of combustion of hydrocarbon C_(x)H_(y) is ''a'' calories and heat of formation of CO_(2) and H_(2)O are ''b'' and 'c' calories respectively then the heat of formation of hydrocarbon C_(8)H is (in calories)
Answer» `XA + YC -B` `xb + yc -a` `b + xc - xa` `xb + (y)/(2) c-a` Solution :`C_(x) H_(y) + (x + (y)/(4)) O_(2) RARR xCO_(2) + (y)/(2) H_(2)O` `Delta H_("comb") = x Delta H_(f_(CO_(2))) + (y)/(2) Delta H_(f_(H_(2)O)) - Delta H_(f_(C_(x)H_(y)))` `a= xb + (y)/(2) C- Delta H_(f_(C_(x)H_(y)))` `Delta H_(f_(C_(x)H_(y))) = xb + (yc)/(2) - a`