# Acid equilibria with delta G

1. May 12, 2014

### yolo123

Hello Forum!
I have this review package for my final full of weird mistakes. Problem is that it is hard for me to know if the solutions are right or not:
Could you please look at this problem I attached?

They bizarrely switch from HA to HB. Is that just a typo?

Then, the sign of DG° seems to be wrong! We are looking at the forward reaction, ie it is positive!

I have my final very soon. Any help is appreciated!

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2. May 12, 2014

### Qube

Where is HA? I do not see it in your attached picture.

3. May 12, 2014

### yolo123

I attached two pictures, one is really tiny. Sorry about that.

4. May 12, 2014

### Qube

The HA is a typo. The work backs it up. Your teacher means HB.

5. May 12, 2014

### Qube

Also what do you think the sign on delta G standard should be and why?

6. May 12, 2014

### Staff: Mentor

It looks like a typo in the problem statement.

Chet

7. May 12, 2014

### yolo123

Hmm.. I may have been mistaken. Tell me if I make sense:
So we use Ka (dissociation of HA). Plug that into -RTln(Q)=DG°.
Now, I must reverse the sign because I'm looking at the REVERSE process.
In the end, I get a negative result, which confirms my teacher's answer!

8. May 12, 2014

### Qube

I would say that because your teacher uses double headed arrows, he's referring to an equilibrium, and therefore delta G should be 0. But this isn't relevant because your teacher refers to delta G standard.

Last edited: May 12, 2014
9. May 12, 2014

### Staff: Mentor

This is not correct. ΔG should be zero, not ΔG standard.

Chet

10. May 12, 2014

### Qube

Good point! I'll fix it.

11. May 12, 2014

### yolo123

So, was my final response right6?