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Question 63

When calcium turnings are heated in a crucible, they react with oxygen in the air to form calcium oxide, CaO\text{CaO}CaO.

A class of students investigated the relationship between the mass of calcium heated and the mass of calcium oxide formed.

Each student was given a different mass of clean calcium turnings to heat. The students used the following method:

  • Weigh a crucible and its lid.
  • Place the calcium turnings in the crucible, replace the lid, and reweigh.
  • Heat the crucible strongly, lifting the lid from time to time.
  • Allow the crucible and lid to cool and reweigh.
  • Repeat the heating, cooling, and reweighing until two consecutive masses are the same.
  • Calculate the mass of calcium oxide formed.
a.

Why is it necessary to lift the lid from time to time while heating?

[1]
b.

Why is it necessary to repeat the heating until two consecutive masses are the same?

[1]
c.

Show how the mass of calcium oxide formed can be calculated from the readings obtained.

[1]
d.

The results of each student's experiment are given in the table below:

Mass of calcium (g)Mass of calcium oxide (g)
0.500.70
1.001.40
1.502.50
2.002.80
2.503.50
3.004.20

Identify the anomalous result by stating the mass of calcium for which it occurred.

[1]
e.

Use the consistent results from the table to calculate the mass of calcium oxide formed when 1.65 g1.65\text{ g}1.65 g of calcium is completely reacted.

[2]

Chemical formulae, equations and calculations Questions

  1. IGCSE
  2. /Chemistry
  3. /Chemical formulae, equations and calculations