Question 2A
C is an Inorganic Compound.
D is an inorganic compound.
Carry out the following exercises on C and D.
Record your observations and identify any gas(es) evolved. State the conclusions you draw from the results of each test.
(a) Put C Into a test tube and add about 5 cm3 of distilled water and shake well. Divide the solution into two portions.
(i) Test the first portion with a litmus paper.
(ii) To the second portion, add about 1 cm of Fehling’s solution, A and B and heat.
(b) Divide D into two portions.
(i) Put the first portion into a dry boiling tube and heat and then allow to cool.
(ii) Add about 5 cm3 of dilute HCl to the second portion and heat, allow it to cool and filter necessary. Divide the resulting solution into two portions.
(ii) To the first portion from 2(b)(ii), add NaOH(aq) in drops and then in excess.
(iii) To the second portion from 2(b)(ii), add aqueous NH3 in drops and then in excess.
Observation
This question was attempted by majority of the candidates and their performance was above average.
In part (a), majority of the candidates tested the find portion of the solution with litmus paper, but some of them did not write the correct inference.
In part (b), majority of the candidates did not adhere to the instructions, and made them to lose marks.
The expected answers include:
C= Glucose D =ZnO
|
TEST |
OBSERVATION |
INFERENCE |
(a) |
C + distilled water |
Dissolved to form |
C is a soluble |
(i) |
C(aq) + litmus paper |
No effect on litmus papers |
Solution of C is neutral |
(ii) |
C(aq) + Fehling’s solution + heat |
A brick-red precipitate is formed |
Reducing sugar/ reducing agent is present |
b(i) |
D + heat |
Solid turned yellow when |
ZnO present
|
(ii) |
D + HCl(aq) |
D dissolved to form a colourless solution |
D is a base/basic oxide |
(iii) |
1st portion from b(ii) |
A white gelatinous precipitate formed, |
Zn2+, Al3+ |
(iv) |
2nd portion from b(ii) |
White gelatinous |
Zn2+, Al3+ Zn2+ is present |