Unformatted text preview: reaction = ∑ nΔH f (products)  ∑ mΔH f (reactants.) Note: the symbol ∑ means “the sum of”. n is the coefficient of the product. m is the coefficient of the reactants. At first this might look complicated, but it is quite simple. It just means you subtract the enthalpies of formation of the reactants from the enthalpies of formation of the products (multiplying each by its coefficient in the balanced reaction). Balanced equation: H 2 C=CH 2 + H 2 → H 3 CCH 3 Using the balanced equation, and plugging in values from the book we get the following: 1(84.68) – [1(52.3) + 1(0)] = 137. Since H 2 is in its standard state, its ΔH f is 0....
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 Fall '08
 Herron,S
 Enthalpy, Reaction, Standard enthalpy change of formation, total enthalpy change, gas forms ethane

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