How many grams of sodium sulfate, g Na2SO4,

Question

How many grams of sodium sulfate, g Na2SO4, must be provided to prepare a 2.35% (m/m) sodium sulfate solution using 135 grams of water?

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Answer 1

2.35% (m/m) means 2.35 percent Na₂SO₄ by mass.

This means 2.35 g Na₂SO₄ per 100 g of solution.

But recall that the 100 g of solution is not only the water, but also includes the grams of Na₂SO₄, and since we have 135 g solution we can write the expression as...

x g Na₂SO₄ /(135 g + x g) solution = 2.35 g Na₂SO₄ / 100 g solution

x/135 + x = 2.35/100

100x = 317.25 + 2.35x

97.65x = 317.25

x = 3.25 g Na₂SO₄ needed

Check:

mass Na₂SO₄ = 3.25 g

Total mass of solution = 3.25 g + 135 g = 138.25 g solution

%(m/m) = 3.25 g / 138.25 g (x100) = 2.35% √