alleryMolality of a solution containing 2.5 g of ethanoic acid (CH₃COOH, M = 60 g/mol) in 75 g of benzene is closest to
A0.278 m
B0.333 m
C1.000 m
D0.556 m
Answer & Solution
Correct answer: D. 0.556 m
1. Moles of CH₃COOH = 2.5 / 60 = 0.0417 mol.
2. Mass of benzene (solvent) in kg = 75 / 1000 = 0.075 kg.
3. Molality = 0.0417 / 0.075 = 0.556 mol/kg.
4. So the solution is 0.556 m in ethanoic acid.
_Source: syllabus Chemistry, Unit 1 "Solutions", Example 1.3_
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