27
QuizMultiple Choice

Measures of Concentration: Molality and Other Calculations — Quiz

Question 27 • Chemistry

A solution is made by dissolving 373 point 5 g of Pb open paren NO sub 3 close paren sub 2 (molar mass: 331 point 2 g over mol in 2 point 0 0 times 10 cubed g of water. What is the molality of the solution? Use molality is equal to moles of solute over kilograms of solvent

Answer
A
0 point 5 6 4 m
B
0 point 4 4 3 m
C
187 m
D
166 m

Explanation

First find the moles of Pb(NO₃)₂: 373.5 g ÷ 331.2 g/mol ≈ 1.128 mol. Convert the water to kilograms: 2.00 × 10³ g = 2.00 kg. Molality is moles of solute divided by kilograms of solvent, so 1.128 mol ÷ 2.00 kg ≈ 0.564 m, which is choice A.

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