Question

Why will ethanol dissolve in water and carbon tetrachloride will not?

Answer 1

Because ethanol is capable of hydrogen bonding, and carbon tetrachloride is not.

Explanation:

Ethyl alcohol is almost a water molecule, `H_3C-CH_2OH`, and so is `H_3COH`; both molecules are capable of interaction with water by hydrogen bonding, and both molecules are infinitely miscible in water. In effect, the lower alcohols are half a water molecule. On the other hand, carbon tetrachloride is a non-polar molecule, and will exhibit very poor water solubility.

Note that with respect to the solubility of alcohols, as the alcohol chain gets longer, non-hyrdoxylic interactions become more important. Propanol and butanol have limited water solubility, as do the higher alcohols.

A more interesting question is whether methanol or ethanol dissolves in carbon tetrachloride. It is a fact that ethanol dissolves in petroleum ether, whereas methanol does not, and for the reasons given above. This is an experiment I'm going to do when I get into the lab.