Chemistry Paper 3 WASSCE (PC), 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: