Answer:
a) 
b) 
c) 
Explanation:
Hello,
In this case, in each reaction we must subtract the Gibbs free energy of formation the reactants to the Gibbs free energy of formation of the products considering each species stoichiometric coefficients. In such a way, the Gibbs free energy of formations are:

So we proceed as follows:
a)

b)

c)

Regards.
Answer:
The answer is B
[The extracting solvent should be non-toxic and readily available]
Explanation:
The extracting solvent should not pose a risk to life (or the risk have to be minimum) and be available in large quantity.
A. Most of the extracting solvents are volatile, and is a good think because you can remove them by distillation.
C. The extraction solvent should <u>not</u> react with the solute, because you lose the extracted compound.
D. The extraction solvent should <u>not</u> be miscible with water. Usually you extract compounds organic compounds from water using an appropriate extracting solvent.