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constants for water
hvap 40.65 kj/mol
hf -285.83 kj/mol
hfusion 6.03 kj/mol
specific heat 4.186 j/gc
molar mass 18.02 g
how much energy is generated from freezing 2.5 g water?

a. 2.5 g 1 mol/18.02 g (285.83) kj/mol
b. 2.5 g 1 mol/18.02 g 4.186 kj/mol
c. 2.5 g 1 mol/18.02 g 40.65 kj/mol
d. 2.5 g 1 mol/18.02 g (-285.83) kj/mol

When it comes to physical changes like phase changes, there are two types of heat energy: sensible heat and latent heat. Sensible heat is the heat absorbed/released when you heat the substance but it doesn't change phase. An example would be heating lukewarm water. The substance is liquid all throughout. Latent heat, on the other hand, is the heat absorbed/released when there is a phase change. An example would be boiling water, because it changes liquid to vapor. 

Hence, for freezing liquid, you use the latent heat, specifically the heat of fusion. The answer should be

2.5 g * (1 mol/18.02 g) * 6.03 kJ/mol = 0.84 kJ/mol

The answer is not in the choices. You only use Hvap if you boil water.

For cyclohexane compounds drawn in a chair conformation:   -axial bonds are vertical  -equatorial bonds are parallel to two bonds within the ring.  thus, as i assume the chair conformation is drawn:   -the x group is in an axial position, as are the five other vertical bonds.  -three axial bonds are on the top face of the ring  -the other three axial bonds are on the bottom face  the position of the second substituent on each ring carbon is equatorial.  gauche groups must be on an adjacent carbon such as carbon 6 and carbon 2, and also gauche groups are rotated by 60 degrees relative to each other.  drawing the newman projections for c1–c2 and c1–c6 aids in visualizing the groups that are gauche to the y group on c1.  click this link and watch some academic videos that may you more understand the topic