## 5J 15.

$\Delta G^{\circ}= \Delta H^{\circ} - T \Delta S^{\circ}$

$\Delta G^{\circ}= -RT\ln K$

$\Delta G^{\circ}= \sum \Delta G_{f}^{\circ}(products) - \sum \Delta G_{f}^{\circ}(reactants)$

ckilkeary 2G
Posts: 68
Joined: Fri Aug 09, 2019 12:16 am

### 5J 15.

So I tried to do the question 5J 15. which is as follows:

Calculate the equilibrium constant at 25C and at 150C for each of the following reactions, using data available in appendix 2A:
NH4Cl(s)<->NH3(g)+HCl(g)

However I got the wrong answer so if someone could look over this and tell me where I went wrong it would be very much appreciated.

First I used appendix 2A and got the ΔG of the reaction by using the formula ΔGrxn=ΔGproducts - ΔGreactants (the number I got was 81.07 kJ/mol)

Then I used ΔG = -RT lnK , (R=8.314, ΔG=81070, T=298) to solve for K and got 6.2 x 10^-15 instead of what the solutions say as 1 x 10^-16

Harry Zhang 1B
Posts: 101
Joined: Sat Sep 14, 2019 12:16 am

### Re: 5J 15.

You might have used the wrong units. The G given in the appendix is in kJ but if you are using 8.314 as your R, convert kJ to J. Your standard G is wrong. You should check your calculations and see if you still have that number. I got 91.12 kJ/mol and this will give the answer in the solutions manual. From there, you can use the vanthoff equation to calculate the K at 150C.

Return to “Gibbs Free Energy Concepts and Calculations”

### Who is online

Users browsing this forum: No registered users and 2 guests