Question 2B
G is an inorganic salt. Carry out the following exercises on G
Record your observations and identify any gas(es) evolved.
State the conclusions you draw from the results of each test.
(a) Dissolve all of G in about 10 cm3 of distilled water in a boiling tube
(b) (i) Test the resulting solution with litmus paper.
(ii) To about 2 cm3 portion of the solution in a test tube, add NaOH(aq). Then
warm the resulting mixture gently.
(iii) To another 2 cm3 portion of the solution, add dilute HNO3.
(Iv) To 2cm3 portion of the solution, add BaCl2(aq) followed by excess dilute HNO3.
Observation
The performance of the candidates was below average in this question.
In part (a), majority of the candidates dissolved G in about 10 cm3 of distilled water in a boiling tube.
In part (b), majority of the candidates did not adhere to the instructions, and this affected their performance.
The expected answers include:
|
TEST |
OBSERVATION |
INFERENCE |
(a) |
G + distilled water |
Colourless solution obtained |
|
(b) |
Solution of G + litmus papers |
Turn red litmus blue
|
G(aq) is alkaline/ basic |
(c) |
Solution of G + NaOH(aq) |
|
Gas is NH3 from NH4+ |
(i) |
Solution of G + HNO3(aq) |
Effervescence, gas evolved
|
Gas is CO2 from |
(ii) |
Solution of G + BaCl2(aq) |
White (Chalky) precipitate formed |
CO32- SO32- SO42- CO32- present |