What is the molarity (M) of a 2.0% (w/v) NaCl solution?

Answer 1

2.0% (w/v) NaCl means 2.0 grams NaCl per 100 mls solution.

Molarity = moles per liter of solution.

So, we need to change 2.0 g / 100 ml to moles / L

molar mass NaCl = 58.4 g / mole

moles NaCl in 2.0 g = 2.0 g x 1 mol / 58.4 g = 0.034 mols NaCl

liters in 100 mls = 100 mls x 1 L / 1000 mls = 0.100 L

Molarity of a 2.0% (w/v) NaCl solution = 0.034 mol / 0.100 L = 0.34 M