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 +
A portion of the filtrate +
A portion of the filtrate + A portion of the filtrate + A portion of the filtrate + |
White (chalky) precipitate
…………………………..
………………………….. …………………………..
…………………………..
………………………….. |
………………….
………………….
…………………………..
………………………….
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 |
……………………………. |
……………………. 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: