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Calculate the molality of a 20% (w/w) aqueous glucose solution. (Molar mass of glucose = 180 g/mol.)

1. 25/18 m
2. 10/9 m
3. 25/9 m
4. 5/18 m

Correct answer: 25/18 m

Solution

Moles of glucose = 20/180; water = 0.080 kg; molality = (20/180)/0.080 = 25/18 m.

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