What is the molarity of a 650. mL solution containing 64 grams of NaCl?

Molarity (M) is defined as moles of solute per liter of solution. So, find the moles; find the liters, and divide to get M.

moles of NaCl = 64g x 1 mole/58.4 g = 1.095 moles NaCl

liters of solution = 650.0 ml x 1 L/1000 ml = 0.6500 liters

Molarity (M) of NaCl = moles/liters = 1.095 moles/0.6500 liters = 1.68 molar = 1.7 M (to 2 significant figures)