I am not 100% sure about a) but I definitely need help on rest please.

a)    Which solution of salt (NaCl or CaCl2) is better to use on icy roads? Why?

CaCl2 would be better as it decreases the freezing point of water more than NaCl in equal concentrations due to the number of ions produced.

b)    What is the concentration of the exact composition of the rock salt/water solution used on icy roads?

c)    Why were we not able to use this composition in our experiment?

d)    How would the results from this experiment be different if water did not form hydrogen bonds?