Page 141 - Chemistry_Form_2

Chemistry
for Secondary Schools

vapour. A red litmus paper turns blue due to the basic condition of ammonia
gas in the solution. Table 5.10 summarises the behaviour of some carbonates on
heating.

Table 5.10: Effects of heat on some carbonate salts
FOR ONLINE READING ONLY
Carbonate salt Behaviour on heating
Potassium carbonate and sodium Do not decompose
carbonate

Calcium carbonate, magnesium Decompose into corresponding metal
carbonate, zinc carbonate, iron(II) oxides and carbon dioxide gas
carbonate, lead(II) carbonate, and
copper(II) carbonate
Ammonium carbonate Decomposes into ammonia gas, carbon
dioxide gas, and water

Activity 5.12

Aim: To investigate the effects of heat on carbonate salts

Requirements: Sodium carbonate, magnesium carbonate, calcium carbonate,
copper(II) carbonate, zinc carbonate, lead(II) carbonate,
limewater, test tubes, spatulas, heat source, blue litmus paper,
wire gauze, tripod stand, test tube holder and bent delivery tube

Procedure
1. Put a spatulaful of zinc carbonate into a dry test tube.
2. Hold the test tube with a test tube holder and heat over a non-luminous
flame.
3. Pass the gas evolved into a test tube of limewater. Record the results.

4. Put a moist blue litmus paper at the mouth of the test tube, and record the
observations.
5. Observe the colour change of the compound when hot and when cold.
6. Repeat Steps 1–5 for the other carbonates. Record all the observations.

Questions
1. What differences were observed when heating zinc carbonate and sodium
carbonate?
2. What is common when heating magnesium carbonate and copper(II)
carbonate?

134 Student’s Book Form Two

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CHEMISTRY FORM TWO NEW 2025 DUMMY.indd 134