Question

A solution contains 6.0micro mol Na2SO4 in 250ml. How many mg/L sodium does it contain?

Answer 1

Answer:

6.0μmol of Na₂SO₄ in 250mL solution contains 1.104 mg/L of sodium atoms.

Explanation:

Given that,

      number of moles of Na₂SO₄ = 6×10⁻⁶mol.

                      volume of solution = 250mL = 0.25L

            Na₂SO₄    →    2Na⁺ +  SO₄²⁻

 so 1 mole of Na₂SO₄ gives 2 moles of Na⁺ ions.

Therefore,

        moles of Na = 2×6×10⁻⁶ = 1.2×10⁻⁵ mol.

molar mass of Na = 23g/mol.

         mass of Na =moles of Na × molar mass of Na

⇒                           = 1.2×10⁻⁵ × 23 = 2.76×10⁻⁴g = 0.276mg

concentration of Na = mass of Na / liters of solution

⇒                               =0.276mg / 0.25L = 1.104 mg/L

The required answer is 1.104mg/L