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For a 2 M aqueous MgCl2 solution with solution density 1.09 g/mL, identify the incorrect statement(s). (Molar mass MgCl2 = 95 g/mol)

1. Molality of Cl- is 4.44 m
2. Mole fraction of MgCl2 is exactly 0.035
3. The concentration of MgCl2 is 19% w/v
4. The concentration of MgCl2 is 19 x 10⁴ ppm

Correct answer: Mole fraction of MgCl2 is exactly 0.035

Solution

Molality of MgCl2 = 2.22 m so Cl- molality = 4.44 m (correct); %w/v = 190/1000*100 = 19% (correct); ppm = 190/1090*10⁶ ~ 1.74x10⁵, not 19x10⁴ = 1.9x10⁵; mole fraction = 2.22/(2.22+50) ~ 0.0425, not 0.035. The cleanly false 'exact' claim is the mole fraction value.

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