Question

Make 500 ml of 15mM NaCl from a 250 mM NaCl stock

Answer 1

n (NaCl)₁ = n (NaCl)₂

C_M = n/V

n = C_M x V

n (NaCL) = 0.015 x 0.500 = 0.0075 mol

n = m/M

V₁ (NaCl) = n/CM = 0.0075/0.25 = 0.03 L = 30 ml

Answer: Take 30 ml of 250 mM solution and make up with distilled water to 500 ml.