WhatsApp Us
Home › TYS Solutions › O Level Chem › 2024 › P1 Q16

2024 O Level Chem P1 Q16 — Stoichiometry / Yield Solution

Stoichiometry / Yield 2024 O Level Pure Chemistry · Paper 1 · Q16

Question

In the reaction between 23g of ethanol and excess hydrogen bromide, the mass of bromoethane obtained is 27g. C₂H₅OH + HBr → C₂H₅Br + H₂O. What is the % yield of bromoethane? [Mᵣ: C₂H₅OH, 46; C₂H₅Br, 109]
  1. A42%
  2. B50%
  3. C59%
  4. D85%
Correct answer: B

Video Solution

Explanation

Answer: B. Calculate moles of starting ethanol and theoretical moles of product.

Moles of \(\text{C}_2\text{H}_5\text{OH}\) = 23/46 = 0.500 mol.

From the 1:1 stoichiometry of \(\text{C}_2\text{H}_5\text{OH} + \text{HBr} \rightarrow \text{C}_2\text{H}_5\text{Br} + \text{H}_2\text{O}\), the theoretical moles of bromoethane = 0.500 mol.

Theoretical mass of \(\text{C}_2\text{H}_5\text{Br}\) = \(0.500 \times 109 = 54.5\) g.

%yield = \(\frac{27}{54.5} \times 100\% \approx 49.5\%\), which rounds to 50%.

Get the Sec 3 / Sec 4 recording package

Every O Level Pure Chemistry TYS MCQ solution video, plus full Sec 3 / Sec 4 topic recordings.

Find out more