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# A Level Chemistry Enthalpy Change Question Help Please! watch

1. Hi guys. I’m struggling with question two. The answer is in the back of the book as -2280kj mol-1, but I don’t know how you’d get to that answer!!

2. Okay, I'm in the same boat as OP. I'm currently lacking practice.
However, I assume that 1.29g of pentane combusted would produce 34.2kJ of energy. Therefore, the enthaly change of combustion requires us to know how much energy one mole of pentane produces. Therefore, n = m/mr = 1.29/86 = 0.015mol.
Since 0.015 mol produces 34.2kJ of energy one would assume 1 mole requires 2280 kJ of energy.
Lastly, given that the reaction is exothermic the answer would be -2280 kJ per mole.
Can anyone confirm?
3. (Original post by Grizzelex)
Okay, I'm in the same boat as OP. I'm currently lacking practice.
However, I assume that 1.29g of pentane combusted would produce 34.2kJ of energy. Therefore, the enthaly change of combustion requires us to know how much energy one mole of pentane produces. Therefore, n = m/mr = 1.29/86 = 0.015mol.
Since 0.015 mol produces 34.2kJ of energy one would assume 1 mole requires 2280 kJ of energy.
Lastly, given that the reaction is exothermic the answer would be -2280 kJ per mole.
Can anyone confirm?
4. Thanks guys!!!

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Updated: February 12, 2018
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