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 .

E M B I B E

ALL IN ONE ISC Chemistry CLASS 11>Chapter 6 - Thermodynamics>Chapter Practice>Q 2

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Earn 100

The sign of $∆ G$ for a spontaneous and non-spontaneous process respectively are

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Important Questions on Thermodynamics

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ALL IN ONE ISC Chemistry CLASS 11>Chapter 6 - Thermodynamics>Chapter Practice>Q 2

In which of the following reactions, standard reaction entropy change

(∆ S °)

is positive and standard Gibbs energy change

(∆ G °)

decreases sharply with increasing temperature?

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ALL IN ONE ISC Chemistry CLASS 11>Chapter 6 - Thermodynamics>Chapter Practice>Q 4

One kilogram of graphite is burnt in a closed vessel. The same amount of graphite is burnt in an open vessel. Will the heat evolved in two cases be same or different.

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ALL IN ONE ISC Chemistry CLASS 11>Chapter 6 - Thermodynamics>Chapter Practice>Q 5

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