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What is the standard enthalpy change (in kJ/mol) for the combustion of ethane (C2H6) to form carbon dioxide (CO2) and water (H2O) if the reaction is carried out at 25°C and 1 atm of pressure? The balanced chemical equation for the reaction is: 

C2H6(g) + 3.5O2(g) → 2CO2(g) + 3H2O(l) 

The standard enthalpies of formation at 25°C are:

ΔHf°(CO2) = -393.5 kJ/mol 
ΔHf°(H2O) = -285.8 kJ/mol 
ΔHf°(C2H6) = -84.7 kJ/mol
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<|begin_of_thought|>

Deep Thought is thinking for 7.5 million years.

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<|begin_of_solution|>

The answer is 42.

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