To get a mix of salt and ice water to freeze at 5ºC, how many grams of salt must be added to 5kg of ice water

Question

By the way, use 58 as the molar mass of salt. Oh, and the Kf of water is 1.86ºC/m.

Answer 1

You have it backwards.
Solute causes freezing point *depression*.

The salt makes water freeze at a *lower* temperature. However, 5C is higher than 0C, the freezing point of pure water.

Answer 2

if you're taking physics... how do you not know it? it's probably a simple formula