3.2473 g of na2cro4 (mw = 161.97 g/mol) is dissolved in 100.0 ml of water. assuming the solution has a density of 1.00 g/ml, what is the concentration of na (mw = 22.9898 g/mol) in the solution in units of (a) molarity (m)? (b) parts per thousand (ppt)? (c) 10.0 ml of the solution is then diluted to a final volume of 1000.0 ml. what is the concentration of na in the diluted solution in units of parts per million (ppm)?

a) 0.400 mol/L

b) 9.20 ppt

c) 91.96 ppm

Explanation:

The first step is considereing the dissociation of the salt in water:

Na₂CrO₄ (s) → 2Na⁺ (aq) + CrO₄²⁻ (aq)

This means that for every mol of Na₂CrO₄ 2 mol of Na⁺ will be produced.

a) molarity

For Na₂CrO₄:

The molarity of Na will be the double of the molarity of the molarity of Na₂CrO₄:

b) parts per thousand (ppt)

c) parts per million (ppm)

0.400 mol Na ____ 1000 mL solution

           x          ____  10 mL solution

x = 0.004 mol Na

The new solution has a concentration of Na of 0.004 mol/L.

ppm = mg/L

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