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Topic: Thermodynamics  (Read 3985 times)

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Offline kassideys

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Thermodynamics
« on: March 24, 2017, 11:14:16 PM »
Im having trouble with these two problems, any help is greatly appreciated

Consider the following reaction:
C2H4(g)+H2(g)→C2H6(g)
ΔH=−137.5 kJ; ΔS=−120.5 J/K

Calculate ΔG at 25∘C and determine whether the reaction is spontaneous.
Express the free energy change in joules to four significant figures.

Here, I got 256.2 kJ but this is incorrect and I'm not sure what I did wrong after checking my work.


Question 2:
At 25 ∘C the reaction from Part A has a composition as shown in the table below.

Substance   Pressure
(atm)
C2H2(g)   4.15
H2(g)   5.35
C2H6(g)   2.25×10−2

What is the free energy change, ΔG, in kilojoules for the reaction under these conditions?
Express your answer numerically in kilojoules.

I have been given T = 298 K and Delta G = -242.1kJ. And I have also been given the formula,
which is Delta G = dG + RT ln Q.

My original Delta G that I calculated was 1016 J. However, this is wrong and I'm not sure where I went wrong.

Thank you, no matter how I do both calculations I keep getting the wrong answer.
« Last Edit: March 24, 2017, 11:39:41 PM by kassideys »

Offline Borek

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Re: Thermodynamics
« Reply #1 on: March 25, 2017, 04:55:19 AM »
Here, I got 256.2 kJ but this is incorrect and I'm not sure what I did wrong after checking my work.

As long as you have not shown how you arrived at the incorrect answer, we can't point you in the right direction.
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Offline KungKemi

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Re: Thermodynamics
« Reply #2 on: March 25, 2017, 05:25:46 AM »
What equation are you using for Part A?

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