Page 14 - 1202 Question Bank Chemistry Form 4 KSSM

PAPER 3

You are required to determine the empirical formula of magnesium oxide. Referring to the Diagram 1, carry out the
relevant experiment.

The crucible and lid are The crucible, lid and The magnesium ribbon The crucible, lid and
weighed. magnesium ribbon are is heated until it reacts magnesium oxide formed
weighed. completely with oxygen. are weighed when cooled.

©PAN ASIA PUBLICATIONS

Lid
Magnesium
Crucible ribbon White
Magnesium powder
ON Digital ON ON
OFF OFF OFF
balance Heat
Diagram 1

(a) State two observations that can be obtained for the experiment. [2 marks]
(b) State the corresponding inferences based on the observations in (a). [2 marks]
(c) Record the reading to two decimal places for [3 marks]
(i) Mass of crucible with lid: ...............g
(ii) Mass of crucible with lid and magnesium ribbon: ...............g
(iii) Mass of crucible with lid and magnesium oxide when cooled: ...............g
(d) What is the mass of the magnesium and mass of oxygen used in the reaction? [3 marks]
(e) Determine the empirical formula of magnesium oxide. [3 marks]
[Relative atomic mass of Mg = 24; O = 16]
(f) Referring to the answer in (e), determine the number of moles of magnesium that reacts with 2 moles of oxygen
atoms. [3 marks]

Note:
If you are not able to carry out the experiment as described above, you can answer this question using the following
samples of data:

Mass of crucible with lid Mass of crucible with lid and Mass of crucible with lid and
magnesium ribbon magnesium oxide when cooled

Lid
Magnesium
Crucible ribbon White
powder
ON 38.4972 g Digital ON ON
OFF OFF 39.2210 g OFF 39.7025 g
balance

39
Question (a): Question (b):
The observation does not include the change in the figure in electronic balance. Inference is the early conclusion of the observation. It is actually the
logical reason why an observation or phenomenon occurs. SOS TIP

39