Neco Model Questions Vol1 2021 Chemistry Question 10

Practice objective / multiple choice question 10 from the 2021 Neco Model Questions Vol1 Chemistry examination.

Neco Model Questions Vol1 2021 Chemistry Objective / Multiple Choice Hard Difficulty
Question 10 NECO_MODEL_QUESTIONS_VOL1 • 2021 • CHEMISTRY • objective

A 0.250 M solution of an unknown monoprotic carboxylic acid HA (molar mass ≈ 88 g mol⁻¹) has a measured pH of 3.00 at 25 °C. (a) Calculate the acid dissociation constant \(K_a\). (b) Identify the acid, assuming it belongs to the series of saturated fatty acids \(C_nH_{2n+1}COOH\). (c) The acid was prepared by oxidising the corresponding aldehyde \(C_nH_{2n+1}CHO\); the theoretical yield was 0.250 mol of acid. If the titration of the solution with 0.100 M NaOH required 35.0 mL to reach the equivalence point, determine the percent yield of the preparation.

Answer Options

A. (a) 2.0×10⁻⁶; (b) valeric acid (C₅H₁₀O₂); (c) 14 %
Correct Answer B. (a) 4.0×10⁻⁶; (b) butyric acid (C₄H₈O₂); (c) 1.4 %
C. (a) 1.0×10⁻⁵; (b) caproic acid (C₆H₁₂O₂); (c) 4.2 %
D. (a) 5.0×10⁻⁶; (b) propionic acid (C₃H₆O₂); (c) 0.14 %
Correct Answer
B
Correct Option:
(a) 4.0×10⁻⁶; (b) butyric acid (C₄H₈O₂); (c) 1.4 %

About This Question

This is Neco Model Questions Vol1 2021 Chemistry Question 10. It is one of the objective questions from the 2021 Neco Model Questions Vol1 Chemistry examination.

Difficulty level: Hard .

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