150.0 g of NaCl (mm: 58.5 g/mol) is dissolved in 250.0 ml of water calculate the molarity

10.26 M

Explanation:

The definition of molarity is moles per liter. Since we are given the mass, we first convert it into moles. Then, we divide by the amount of liters. A common way to solve the problem is through dimensional analysis. In it, you multiply all the numbers on top and divide by the numbers in the bottom.

150g     |        mol        |                          |    1000 mL

   = 10.26 M

            |     58.5 g       |        250 mL     |       1 L

This is the same as 150 * 1000 / (58.5 * 250) = 10.26M.

You can double check that you get the correct units by crossing out the same units on top and bottom. At the end, you should be left with a mol on top and L in the bottom. mol/L = molarity (M).