| | Form 4: Chapter 3: Describe an experiment in the laboratory to determine the empirical formula of magnesium oxide. Your answer should consist of the following. |
| |
Given that relative atomic mass of Mg = 24, O = 16 [13 marks] |
Suggested Answer:
[Material and apparatus ]
[Magnesium ribbon, sand paper, crucible with lid, tongs, Bunsen burner, tripod stand, pipe-clay triangle and balamce.] or [diagram] 2
[Procedure]
· A crucible and its lid is weighed and its weight is recorded. 1
· A 10 cm length of magnesium ribbon is coiled loosely and is placed in the crucible. 1
· The crucible with its lid and content are weighed again and the weight is recorded. 1
· The crucible is heated strongly without its lid. 1
· When the magnesium starts to burn, the crucible is covered with its lid. 1
· Using a pair of tongs, the lid is lifted at intervals. 1
· When the burning is completed, the lid is removed and
the crucible is heated strongly for 2 minutes. 1
the crucible is heated strongly for 2 minutes. 1
· The rucible is allowed to cool to room temperature. 1
· The crucible and its lid and content are weighed again and its weight is recorded. 1
max 5
[Precautions taken]
· The magnesium ribbon is cleaned with sand paper to remove the layer of magnesium oxide on the surface.
· The crucible must cover with its lid to prevent the white fumes of magnesium oxide of escaping.
· The processes of heating, cooling and weighing are repeated until a constant mass is obtained. [any two of the above] 2
[ Results ]
Crucible + lid = a g
Crucible + lid + magnesium = b g
Crucible + lid + magnesium oxide = c g 1
[ Calculation ]
| Element | Magnesium | Oxygen |
| Mass(g) | b-a | c-b |
| Number of moles of atoms | b-a/24 | c-b/16 |
| Simplest ratio of moles | X | y |
No comments:
Post a Comment