The standard heat of formation ( Δ f H 298 0 ) of ethane (in k J / m o l ), if the heat of combustion of ethane, hydrogen and graphite are –1560, –393.5 and –286 k J / m o l , respectively is .

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Aicharya · Accepted Answer

2C ( graphite ) + 3 H 2 ( g ) → 1 C 2 H 6 + Δ H f ( C 2 H 6 ) (A) C 2 H 6 + 7 2 O 2 → 2C O 2 + 3 H 2 O Δ H C = – 1560 (B) H 2 + 1 2 O 2 → H 2 O Δ H C = – 393 . 5 (C) C(graphite) + O 2 → C O 2 Δ H C = – 286kJ/mol Δ H f ( C 2 H 6 ) = 3 ( – 393 . 5 ) + 2 ( – 286 ) + 156 0 = – 118 0.5 + ( – 572 ) + 156 0 = 192 . 5 2 C g r a p h i t e + 3 H 2 → C 2 H 6 (1) eq n C 2 H 6 + 7 2 O 2 → 2 C O 2 + 3 H 2 O (2) eq n H 2 + 1 2 O 2 → 2 C O 2 + 3 H 2 O (3) eq n C g r a p h i t e + H 2 O → C O 2 (4) eq n To get equation (1) eq n (2) + 2 × eq n (3) 2 × eq n ∆ H f of ethane = 1560 + 2 × - 286 + 3 ( - 393.5 ) = 1560 - 572 - 1180.5 = -192.5

The standard heat of formation ( Δ f H 298 0 ) of ethane (in k J / m o l ), if the heat of combustion of…

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