How many grams of NaCl are required to make 500.0 mL of a 0.25 M NaCl standard solution?

Question

A. 7,250 g NaCl

B. 2.2 g NaCl

C. 7.3 g NaCl

D. 0.0021

Answer 1

0.25 M = 0.25 mol NaCl/liter of solution.

Since you want only 0.500 L (500.0 ml x 1L/1000 ml), the number of moles NaCl needed will be...

0.25 mol/L x 0.5000 L = 0.125 moles

Molar mass of NaCl = 58.44 g/mol

Grams NaCl needed = 0.125 moles x 58.44 g/mol = 7.3 grams NaCl needed (to 2 significant figures) Ans C