# Delta G and equalibrium constant question

1. Oct 31, 2013

### paulnz

1. The problem statement, all variables and given/known data
The equation and data to which the question refers is in the attachment. I am just trying to do part (a) of the question at the moment:

Calculate ΔG and K, the equilibrium constant, for this reaction at 298 K.

2. Relevant equations
I would have thought that I would need to use the equation ΔG=-RTln K, but I am unsure how to find K, the equilibrium constant, because I am not given the amounts of the reactants or products.

3. The attempt at a solution

Perhaps there is a way to solve the problem using an equation I am not aware of? And I am not sure how to use the data given to solve the problem, if in fact it is needed for question (a) I have no idea.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

#### Attached Files:

• ###### delta g and constant.jpg
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2. Oct 31, 2013

### Staff: Mentor

How is the standard free energy of formation of a species related to its standard enthalpy of formation, standard entropy of formation, and standard temperature 298? If you know the free energy of formation of each reactant and each product, how do you calculate the standard free energy change for the reaction?

If you can't answer these two questions, you need to go back to your textbook and find out.

Chet

3. Oct 31, 2013

### paulnz

Thanks, that gave me the direction I needed to go in.

I believe that I use the equation:
$$\Delta _{f}G^{o}=\Delta _{r}H^{o} - T\Delta _{r}S^{o}$$

and take the reactant values from the product? ie:

$$\Delta _{r}G^{o}=\Delta _{f}G^{o}(CuO)-(\Delta _{f}G^{o}(Cu)+\frac{1}{2}\Delta _{f}G^{o}(\frac{1}{2}O_{2}))$$

Last edited: Oct 31, 2013
4. Nov 1, 2013

### Staff: Mentor

You have the right idea. Just one thing: lose the Δ's in your first equation, and, on the right hand side of your second equation.

Chet