Question

Sea water contains 2% salt (NaCl) by weight. Given that water has a

density of 1g/mL. Determine the concentration of salt in:


(a) mg/L , (b) ppm.

Answer 1

Answer:

a) Concentration of salt in mg/L = 2g/100mL

b) concentration in ppm = 20000 ppm

Explanation:

Percentage composition of salt by weight in water = 2%

Density of water = 1 g/mL

100 mL of water will has a mass of 100 g

Mass of salt in 100 g of water = 2% ×100 g = 2 g

Therefore, 2 g of salt is dissolved in 100 mL of solution

Concentration of salt in 100 mL of solution = 2g/100mL

a) Concentration in mg/L

Mass of salt = 2 g = 2000 mg

Volume of solution = 100 mL = 0.1 L

Concentration in mg/L = 2000 mg/0.1 L

Concentration in mg/L = 20000 mg/L

b) Concentration in ppm

1 ppm = 1mg/L

Therefore, concentration in ppm = 20000 ppm