Chemistry Paper 3, Jan-Feb 2021

Question 2

2. The following tests were carried out on solid C. Complete the table.

	TEST	OBSERVATION	INFERENCE
(a)	C+ distilled water, stirred and filtered	C partly soluble	………………….
(b)(i) (ii) (iii) (iv) (v)	A portion of the filtrate + NaOH_(aq) in drops then in excess A portion of the filtrate + NH₃_(aq) in drops then in excess A portion of the filtrate + HCl_(aq) and warmed then allowed to cool A portion of the filtrate + H₂SO₄_(aq) A portion of the filtrate + FeSO₄_(aq) + Conc. H₂SO₄ gently down the sides of the test tube.	White (chalky) precipitate White precipitate soluble ………………………….. ………………………….. ………………………….. ………………………….. ………………………….. ………………………….. …………………………..	…………………. …………………. …………………. ………………………….. …………………………. NO₃- present
(c)(i) (ii)	Residue from 2(a) above + HCl_(aq) Gas form 2(c)(i) bubbled through lime water	Effervescence of colourless, odourless gas ………………………………..	………………………. ………………………. ……………………….
(d)	A portion of the solution Formed in 2(c)(i)+ NH4(aq) in drops then in excess	……………………………. ……………………………..	……………………. Zn²⁺ present

[21 marks]

Observation

This question tested the knowledge of qualitative analysis. Majority of the candidates responded to this question. However, their performance was below average.

In part (a), majority of the candidates could not write correct inference from the given observation.

In part (b), majority of the candidates could not write correct observations and inferences.

In part (c), majority of the candidates could not confirm the gas when bubbled through lime water.

In part (d), majority of the candidates could not write correct observations and inferences.

The expected answers include:

Chemistry Paper 3 WASSCE (PC), 2021

Question 2

Observation