Neco Model Questions Vol1 2023 Chemistry Question 29

Practice objective / multiple choice question 29 from the 2023 Neco Model Questions Vol1 Chemistry examination.

Neco Model Questions Vol1 2023 Chemistry Objective / Multiple Choice Hard Difficulty
Question 29 NECO_MODEL_QUESTIONS_VOL1 • 2023 • CHEMISTRY • objective

Five grams of an unknown monohydric alcohol are dissolved in 200.0 g of water. The freezing point of the solution is lowered by 0.78 °C. (i) Determine the molar mass of the alcohol. (ii) The alcohol contains only C, H and O and its molecular formula follows \(C_{n}H_{2n+2}O\). Find the integer value of \(n\). (iii) Using the molar mass obtained, calculate the boiling‑point elevation when 10.0 g of the same alcohol is added to 500.0 g of water. (Take \(K_f = 1.86\,^{\circ}\text{C·kg·mol}^{-1}\) and \(K_b = 0.512\,^{\circ}\text{C·kg·mol}^{-1}\); assume the van't Hoff factor \(i = 1\)).

Answer Options

A. Molar mass ≈ 72 g mol⁻¹; n = 4; boiling‑point elevation ≈ 0.20 °C
Correct Answer B. Molar mass ≈ 60 g mol⁻¹; n = 3; boiling‑point elevation ≈ 0.17 °C
C. Molar mass ≈ 54 g mol⁻¹; n = 3; boiling‑point elevation ≈ 0.15 °C
D. Molar mass ≈ 48 g mol⁻¹; n = 2; boiling‑point elevation ≈ 0.12 °C
Correct Answer
B
Correct Option:
Molar mass ≈ 60 g mol⁻¹; n = 3; boiling‑point elevation ≈ 0.17 °C

About This Question

This is Neco Model Questions Vol1 2023 Chemistry Question 29. It is one of the objective questions from the 2023 Neco Model Questions Vol1 Chemistry examination.

Difficulty level: Hard .

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