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2017 O Level Chem P1 Q1 — Experimental Techniques / Drying and Collecting Gases Solution

Experimental Techniques / Drying and Collecting Gases 2017 O Level Pure Chemistry · Paper 1 · Q1

Question

A student is provided with two drying agents: concentrated sulfuric acid and calcium oxide. Which method should he use to collect a sample of dry ammonia? Question diagram

Question diagram

A
B
C
D

Correct answer: D

Video Solution

Explanation

Answer: D. Ammonia is an alkaline gas, so it must be dried with calcium oxide, not concentrated sulfuric acid (which would react with it). Ammonia is also less dense than air, so it is collected by upward delivery into an inverted container.

Only D uses calcium oxide and collects by upward delivery. A and B use concentrated sulfuric acid (the wrong drying agent for an alkaline gas), and C uses calcium oxide but the wrong collection method.

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