PCAT Chemical Processes – Hypothetical Reaction
- Mar 20, 2018
- PCAT Question of the Day
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Remember that to be spontaneous, a reaction must have a ΔG that is negative. To answer this question, start with the Gibbs Free Energy equation:
ΔG = ΔH – TΔS
The reaction starts with two moles of gas and ends with three moles of gas, so the ΔS is positive. ΔH is given as a positive number in the question. The equation now looks like this:
ΔG = (+) – T(+)
To make ΔG negative and the reaction spontaneous, we want a large T so that we’re subtracting a large positive number. Thus the answer is (D).
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