I cannot figure out this problem. It says to "Calculate the mole fraction of MgCl2 (subscript 2) in a solution created by dissolving 132.1 g of MgCl2 in 175 mL of water."

Question

I started by converting 132.1g to moles, but I got stuck when I tried to convert 175mL to moles.

For reference, the answer given in the back of the book is 0.125

Answer 1

You started correctly.
mols MgCl2 = grams/molar mass = ?
mols H2O = grams H2O/molar mass H2O. We assume that the density of H2O is 1 g/mL so 175 mL H2O has a mass of 175 g.
total mols then is mols MgCl2 + mols H2O.
I assume you know how to do the remainder.