Waec Model Questions Vol1 2021 Chemistry Question 20

Practice objective / multiple choice question 20 from the 2021 Waec Model Questions Vol1 Chemistry examination.

Waec Model Questions Vol1 2021 Chemistry Objective / Multiple Choice Hard Difficulty
Question 20 WAEC_MODEL_QUESTIONS_VOL1 • 2021 • CHEMISTRY • objective

A solution is prepared by dissolving 5.00 g of methanol (CH₃OH, M = 32.04 g mol⁻¹) in 100.0 g of water. The observed boiling point of the solution is 100.5 °C. Assuming the boiling‑point elevation follows \(\Delta T_b = i\,K_b\,m\) with \(K_b\) for water = 0.512 °C·kg mol⁻¹ and that methanol does not ionise (i = 1), (a) calculate the expected boiling‑point elevation and state whether the observation is consistent; (b) if not, determine the apparent molal boiling‑point constant \(K_{b,\text{app}}\) that would give the observed elevation.

Answer Options

Correct Answer A. a) Expected ΔTb = 0.799 °C (predicted boiling point 100.799 °C) - observation not consistent. b) Kb,app = 0.320 °C·kg·mol⁻¹
B. a) Expected ΔTb = 0.799 °C (predicted boiling point 100.799 °C) - observation consistent. b) Kb,app = 0.512 °C·kg·mol⁻¹
C. a) Expected ΔTb = 0.256 °C (predicted boiling point 100.256 °C) - observation not consistent. b) Kb,app = 0.128 °C·kg·mol⁻¹
D. a) Expected ΔTb = 1.024 °C (predicted boiling point 101.024 °C) - observation not consistent. b) Kb,app = 0.256 °C·kg·mol⁻¹
Correct Answer
A
Correct Option:
a) Expected ΔTb = 0.799 °C (predicted boiling point 100.799 °C) - observation not consistent. b) Kb,app = 0.320 °C·kg·mol⁻¹

About This Question

This is Waec Model Questions Vol1 2021 Chemistry Question 20. It is a objective / multiple choice question from the 2021 Waec Model Questions Vol1 Chemistry examination.

Difficulty level: Hard .

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