Calculate the enthalpy of formation of methane from the following data. C ( s ) + O 2 ( g ) → CO 2 ( g ) ; Δ r H = − 393 . 5 k J H 2 ( g ) + O 2 ( g ) → 2 H 2 O ( l ) ; Δ r H ° = − 571 . 8 k J CH 4 ( g ) + 2 O 2 ( g ) → CO 2 ( g ) + 2 H 2 O ( l ) ; Δ r H ° = − 890 . 3 k J

Given:- C ( s ) + O 2 ( g ) → CO 2 ( g ) ; Δ r H = − 393 . 5 k J .....(1) H 2 ( g ) + O 2 ( g ) → 2 H 2 O ( l ) ; Δ r H ° = − 571 . 8 k J .....(2) CH 4 ( g ) + 2 O 2 ( g ) → CO 2 ( g ) + 2 H 2 O ( l ) ; Δ r H ° = − 890 . 3 k J .....(3) Adding eqn (1), (2) & (3), we have C ( s ) + 2 H 2 ( g ) ⟶ CH 4 ( g ) , Δ f H = − 75 k J Hence, the enthalpy of formation of methane is − 75 k J .

Calculate the enthalpy of formation of methane from the following data. C ( s ) + O 2 ( g ) → CO 2 ( g ) ; Δ r H = − 393 . 5 k J H 2 ( g ) + O 2 ( g ) → 2 H 2 O ( l ) ; Δ r H ° = − 571 . 8 k J CH 4 ( g ) + 2 O 2 ( g ) → CO 2 ( g ) + 2 H 2 O ( l ) ; Δ r H ° = − 890 . 3 k J

Given:- C ( s ) + O 2 ( g ) → CO 2 ( g ) ; Δ r H = − 393 . 5 k J .....(1) H 2 ( g ) + O 2 ( g ) → 2 H 2 O ( l ) ; Δ r H ° = − 571 . 8 k J .....(2) CH 4 ( g ) + 2 O 2 ( g ) → CO 2 ( g ) + 2 H 2 O ( l ) ; Δ r H ° = − 890 . 3 k J .....(3) Adding eqn (1), (2) & (3), we have C ( s ) + 2 H 2 ( g ) ⟶ CH 4 ( g ) , Δ f H = − 75 k J Hence, the enthalpy of formation of methane is − 75 k J .