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:
A molecule is tetrahedral if the central atom has four bonds and no lone pairs.
Explanation:
A typical example is a molecule of methane (see image).
The electron pairs in the bonds repel the electrons in the other bonds, so they all try to get as far from each other as possible.
They can do this if the bonds point to the corners of a tetrahedron, with bond angles of 109.5°.
Answer:
the answers are either a or d
Explanation:
Answer:
A solution was NOT formed.
Explanation:
For a solution to be formed, the green powder would need to dissolve in the water to form a homogenous mixture. But since the water was cloudy and had lumps of the green powder, it means that the powder did not dissolve, but instead remained insoluble.
A medium can be anything that a wave can pass through e.g the medium can be solid objects, air, water, etc.