# Homework Help: Thermochemistry significance of infinitely dilute solution

1. Dec 15, 2012

### Saitama

Thermochemistry significance of "infinitely dilute solution"

1. The problem statement, all variables and given/known data
(see attachment)

2. Relevant equations

3. The attempt at a solution
I don't know where to start from and it seems to me that data given is insufficient to solve this problem. Also, what's the significance of "infinitely dilute solution"?

Any help is appreciated!

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2. Dec 15, 2012

### Staff: Mentor

Re: Thermochemistry

Infinitely diluted means all activities equal 1 (so no need for calculations of ionic strength and activity coefficients).

Can't say I understand the question.

3. Dec 15, 2012

### epenguin

Re: Thermochemistry

Nor me. I'm inclined to say it should be zero for infinitely dilute solutions.

4. Dec 15, 2012

### Saitama

Re: Thermochemistry

Is the question wrong then?

5. Dec 15, 2012

### epenguin

Re: Thermochemistry

Is ΔFf0 defined in your text?

Usually ΔF0 's are defined for a process not a substance, but perhaps there is a convention I am out of date about.

6. Dec 15, 2012

### Saitama

Re: Thermochemistry

ΔFf0? No, there is no such thing in my text.

7. Dec 16, 2012

### Saitama

Re: Thermochemistry

Can you tell me what does ΔFf0 mean? I will try to look it up somewhere.

8. Dec 16, 2012

### Staff: Mentor

Re: Thermochemistry

I wonder if epenguin really means ΔFf0, or did he just misread the problem. F is sometimes used for Helmholtz free energy, but I think question lists ΔHf0 - enthalpies of formation.

9. Dec 16, 2012

### epenguin

Re: Thermochemistry

Typo from not being able to see original on same screen as typing, I meant ΔHf0

10. Dec 16, 2012

### Saitama

Re: Thermochemistry

I know what ΔHf0 means but to solve this question, I think the data is insufficient or am I missing something?

11. Dec 18, 2012

### Saitama

Re: Thermochemistry

Can I get some more help?

12. Dec 18, 2012

### doub

Re: Thermochemistry

You have all the info I believe...Look at hess's law and at the net ionic equation. I have posted what I believe the answer to be...

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13. Dec 19, 2012

### Staff: Mentor

Re: Thermochemistry

Please don't give final answers, that's not how the forum works.

When you mix diluted solutions there will be no precipitate. So while you can be right guessing what the question author had on mind, it is not a correct answer to the question as worded.

14. Dec 20, 2012

### epenguin

Re: Thermochemistry

I don't know what ΔHf0 quite means, I'd have to guess so I can't help. But these questions generally involve a cycle, were the Δ's add up to zero if you go round it, and there is one step you have to find the Δ of when given all the others.

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