JAMB Chemistry 2019 Objective — Question 34

Question 34 of 40 from the Joint Admissions and Matriculation Board (JAMB) Chemistry 2019 Objective paper, with the correct answer and a full explanation.

Water is poured over a white solid and a colourless, neutral gas is evolved which burns with a very smoky flame. The white solid is

A. Calcium
B. Calcium hydroxide
C. Calcium carbideCorrect
D. Calcium oxide

Explanation

When water is poured over calcium carbide, ethyne (acetylene) gas is evolved (which burns with a smoky flame), leaving a residue of calcium hydroxide/oxide: CaC₂(s) + H₂O(l) → CaO(s) + C₂H₂(g).

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