Given C ( graphite)+O_(2)(g)rarr CO_(2)(g), Delta_(r)H^(@) = - 393.5 kJ mol^(-1)…...(i) H_(2)(g)+ (1)/(2) O_(2)(g) rarr H_(2)O(l), Delta_(r)H^(@) = - 285 .8 kJ mol^(-1)….(ii) CO_(2)(g)+ 2H_(2)O(l) rarr CH_(4)(g) +2O_(2)(g), Delta_(r)H^(@) = + 890 .3 kJ mol^(-1)......(iii) Based on the above thermochemical equations , the valueof Delta_(r)H^(@)at 298 K for the reaction C ( graphite) + 2H_(2)(g)rarr CH_(4)(g) will be

Given C ( graphite)+O_(2)(g)rarr CO_(2)(g), Delta_(r)H^(@) = - 393.5 k

1.	Given C ( graphite)+O_(2)(g)rarr CO_(2)(g), Delta_(r)H^(@) = - 393.5 kJ mol^(-1)…...(i) H_(2)(g)+ (1)/(2) O_(2)(g) rarr H_(2)O(l), Delta_(r)H^(@) = - 285 .8 kJ mol^(-1)….(ii) CO_(2)(g)+ 2H_(2)O(l) rarr CH_(4)(g) +2O_(2)(g), Delta_(r)H^(@) = + 890 .3 kJ mol^(-1)......(iii) Based on the above thermochemical equations , the valueof Delta_(r)H^(@)at 298 K for the reaction C ( graphite) + 2H_(2)(g)rarr CH_(4)(g) will be
Answer» `- 74.8 kJ mol^(-1)` ` -144.0 kJ mol^(-1)` ` + 74.8 kJ mol^(-1)` `+ 144.0 kJ mol^(-1)` Solution :Eqn. (i) `+2 xx ` Eqn. (II)`+` Eqn. (iii) GIVES the required EQUATION with `DELTAH= ( - 393.5)+ 2 ( - 285.8 )+(+ 890.3)kJ mol^(-1)` `= - 74.8 kJ mol^(-1)`