8. A 50.0 mL 0.05 mol/l solution of sodium cloride (NaCl) was mixed with 100.0 mL of 0.02 mol/l NaCl solution. What is the mass percent of NaCl in the final solution?
Assume the volumes are additive and their densities 21 g/mL. The molar mass of
NaCl is 58.5 g/mol. (10 points)

Explanation:

Data:

Solution 1: V₁ =   50.0 mL; c₁ = 0.05 mol·L⁻¹

Solution 2: V₂ = 100   mL; c₂ = 0.02 mol·L⁻¹

NaCl         :   ρ =     2.1 g/mL  

1. Solution 1

(a) Moles of NaCl

(b) Mass of NaCl

(c) Volume of NaCl

(d) Volume of water

V = 50.0 mL - 0.070 mL = 49.9 mL

(e) Mass of water

2. Solution 2

(a) Moles of NaCl

(b) Mass of NaCl

(c) Volume of NaCl

(d) Volume of water

V =100 mL - 0.055 mL = 100 mL

(e) Mass of water

3. Combined solutions

(a) Mass of NaCl

Mass of NaCl = 0.015 g + 0.012 g = 0.018 g

(b) Mass of water

Mass of water = 49.9 g + 100 g = 150 g

(c) Mass percent