How would the vapor pressure of a solution that contains 0.5 mol of cacl2 in 1.0 kg of water compare with the vapor pressure of a solution that contains 1.5 mol of glucose in 1.0 kg of water?

a) one-third as large
b) the same
c) three times as large
d) nine times as large

Option b) the same

Given that Ca Cl2 is a strong electrolyte it will dissolve completely and each mol will produce 3 times the number of mols.

This means that 0.5 mol of CaCl2 will be equivalent to 1.5 mol of ions and then the change of the vapor pressure is the same than that of 1.5 mol / kg glucose.