Part A Calculate the enthalpy change on burning 1 g of H2 (g) to H2O(1) at 25° C

Question

Part A Calculate the enthalpy change on burning 1 g of H2 (g) to H2O(1) at 25° C and 1 bar Express your answer using four significant figures Enthalphy change- kJ/g Submit My Answers Give Up Part B Calculate the enthalpy change on burning 1 g of n-octane(g) to CO2 (g) and H2 O() at 25 °C and 1 bar. Express your answer using five significant figures. Enthalpy changes kJ/g Submit My Answers Give Up Part C Compare H2(gand n-octane (g) in terms of joules of heat available per gram H2 (g) is about 30 times less energetic as a fuel than octane on a weight basis H2 (g) is about 3 times more energetic as a fuel than octane on a weight basis H2 (g) is about 3 times less energetic as a fuel than octane on a weight basis H2 (g) is about 30 times more energetic as a fuel than octane on a weight basis Submit My Answers Give Up

Explanation / Answer

A) H2 + (1/2) O2 -----> H2O(l)

delta H of reaction = delta H of products - delta H of reactants

Delta H = [285.8 ] - [ 0+0]

delta H = -285.8 KJ

Molar mass of H2 = 2 gms

delta H = -285.8 /2 = -142.9 KJ /g

B) C8H18 + (25/2)O2 ------> 8CO2 + 9H2O(l)

delta H = delta Hf of prodcuts - delta Hf of reactants

delta H = [9 x -258 + 8 x 393.509 ] - [-208.4]

delta H = -5261.672 KJ

Molar mass of C8H18 [n-octane] = 114

delta H = -5261.672 / 114 = -46.155 KJ

C) By comparing delta H values of both H2 and Octane, we noticed that

Option (B): H2(g) is about 3 times more energetic as a fuel than octane on a weight basis

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