Engineering
Chemistry
Gibbs Free Energy Calculations and Third Law
Question

What can be concluded about the values of ΔH and ΔS from this graph?

ΔH < 0, ΔS > 0

ΔH > 0, ΔS < 0

ΔH < 0, ΔS < 0

ΔH > 0, ΔS > 0

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Solution

The graph shows ln(K) vs 1/T, which is linear with a negative slope. This relates to the van't Hoff equation: ln(K)=-ΔHR·1T+ΔSR. The slope equals -ΔH/R. A negative slope means -ΔH/R is negative, so ΔH must be positive. The y-intercept is positive, which equals ΔS/R. Therefore, ΔS must also be positive.

Final answer: ΔH > 0, ΔS > 0