What is the molarity (M)of a sodium chloride solution prepared by dissolving 20.0 g of sodium chloride (58.44g/mol) in water to give 45 mL of solution?

Question

What is the molarity (M)of a sodium chloride solution prepared by dissolving 20.0 g of sodium chloride (58.44g/mol) in water to give 45 mL of solution?

Answer 1

Molarity (M) is defined as moles of solute (NaCl) per liter of solution.

45 ml is converted to 0.045 L (45 ml x 1 L/1000 ml = 0.045 L)

Now we need to find the mole of NaCl:

molar mass NaCl = 58.4 g/mol

20.0 g x 1 mol /58.4 g = 0.342 moles

Molarity = 0.342 moles/0.045 L = 7.61 M