WAEC Chemistry Past Questions & Answers

491.

Which of the following compounds will leave a metal residue when heated?

Cu(NO₃)₂

AgNO₃

K₂CO₃

CaCO₃

View answer & explanation

Correct answer is B

No explanation has been provided for this answer.

492.

CuSO₄5H₂O can be obtained from an aqueous solution of copper (ll) tetraoxosulphate (VI) by

evaporation to dryness

using chromatography

precipitation

crystallization

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Correct answer is D

No explanation has been provided for this answer.

493.

Equal amounts of marble chips are reacted separately with 100cm3 of hydrochloric acid of different concentrations. If all the marble chips reacted; which of the following remained the same in each case?

Average rate of evoluton of gas

Total mass of gas evolved during the reaction

Time taken for the reaction to reach completion

Initial reaction rates

View answer & explanation

Correct answer is B

The total mass of gas evolved during the reaction will remain the same in each case. This is because the amount of marble chips is the same in each case, and the reaction goes to completion. Therefore, the same amount of gas will be produced in each case, regardless of the concentration of the hydrochloric acid.

494.

What is the expression for the equilibrium constant (K_c) for the following reaction? N_2(g) + O_2(g) ⇌ 2NO_(g)

\(\frac{[NO^2]}{[N^2] + [O^2]}\)

\(\frac{[2NO]^2}{[N_2][O_2]}\)

\(\frac{[N_2] + [O_2]}{2[NO]^2}\)

\(\frac{[NO]^2}{[N_2][O^2]}\)

View answer & explanation

Correct answer is D

No explanation has been provided for this answer.

495.

What will happen if more heat is applied to the following system at equilibrium?

X\(_2\)(g) + 3Y\(_2\)(g) ⇌ 2XY\(_3\)(g); ∆H = xKJmol\(^{-1}\)