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C1210 lecture 16 - Hesss Law suggests that large databases...

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Hess’s Law suggests that large databases of heats of reaction are useful for predicting heats of reaction for new reactions. Databases include combustion reactions, phase changes, and formation of compounds from elements. Definition : The standard heat of combustion, of a substance is the amount of heat released when one mole of a fuel substance is completely burned in pure oxygen gas and all reactants and products are brought to 25 °C and one bar pressure. All carbon in the fuel becomes CO 2 gas and all hydrogen becomes liquid H 2 O. Combustion reactions are always exothermic, so is always negative for combustion reactions. 0 c H Δ 0 c H Δ
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