Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: peach_hime on September 25, 2019, 04:43:56 PM
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When calculating entropy changes, why don't we convert our values for making one mole? How do I know whether to balance the equation using whole numbers, or can I use fractions?
e.g. Calculate the change in entropy associated with the Haber process for the production of ammonia from nitrogen and hydrogen gas.
At 298K as a standard temperature:
S(NH3) = 192.5 J/mol K
S(H2) = 130.6 J/mol K
S(N2) = 191.5 J/mol K
The correct answer is -198.3 J/K/mol
Why can I not balance the equation to make one mole of ammonia using fractions? I would get -99.5 J/K/mol though and this is not the correct entropy change.
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You would have to keep the stoichiometric coefficient of nh3 as 1