Question

Calculate the Molarity of a 22.00% (wt/wt) solution of sodium sulfate decahydrate (Na2SO4-10H2O). Assume 20 degrees C and the density of the solution is 1.2106 g/mL.

Please show work so that I can learn it

Answer 1

22% wt/wt solution of (Na2SO4-10H2O) means 100g of solution contains 22g of (Na2SO4-10H2O).

In otherwords 100g of solution contains 0.068 moles of (Na2SO4-10H2O).

Because 22g of (Na2SO4-10H2O) = 22 / 322.2 = 0.068 moles

Molecular mass of (Na2SO4-10H2O) = 322.2g

density = mass / volume

Volume = mass / density

Therefore volume of 100g of solution = 100 / 1.2106 = 82.6mL

In otherwords 82.6mL of the solution contains 0.068 moles of (Na2SO4-10H2O)

Molarity = No. of moles / volume in liters

Molarity = 0.068 / 0.0826L = 0.823M

82.6mL = 82.6 / 1000 = 0.0826L