Octane, C_8H_10, burns according to the balanced equation: 2 C_8H_18 (I) + 25 O_

Question

Octane, C_8H_10, burns according to the balanced equation: 2 C_8H_18 (I) + 25 O_2 (g) rightarrow 16 CO_2 (g) + 18 H_2O(l) delta H_rxn = -10,920 kj/mol If an engine burns 277 moles of C_8H_10. what is the heat, q_rxn associated with this reaction? -39.42 kj -78.85 kj -1,510,000 kj -3,030,000 kj -6,050,000 kj What is the value of delta H degree_rxn for the reaction 2 KCl (s) +3O_2(g) rightarrow 2 KClO_3 (s)? delta H degree f for KCIO_3 (s) is -391.20 kj/mol Delta H degree (forKCl (s) is -435.87 kj/mol +89.34 kj/mol - 62.67 kj/mol -89.34 kj/mol -827.02 kj/mol - 1654.14 kj/mol

Explanation / Answer

4) for 2 moles of C8H18 heat released 10920

for 277 moles C8H18 = ( 277/2 ) x 10920 = - 1,510,000 KJ  

Hence optin C

5) dH rxn = dH products - dH reactants

dH rxn = 2 dH KClO3 - 2 dH KCl -3 dH O2 = 2( -391.2) -2( -435.87) -3(0)

     = 89.34 KJ/mol

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