Page 136 - Chemistry_Form_2

Chemistry
for Secondary Schools

Activity 5.10

Aim: To prepare copper(II) sulfate

Requirements: Beaker, evaporating dish, glass rod, wire gauze, measuring
FOR ONLINE READING ONLY
cylinder, filter paper, filter funnel, tripod stand, heat source,
dilute sulfuric acid, and copper(II) carbonate
Procedure

1. Transfer about 25 cm of dilute sulfuric acid into a small beaker and heat
3
gently.

2. Add solid copper(II) carbonate to the beaker containing the hot acid and
stir the mixture by using a glass rod until it is saturated.
3. Filter the mixture and crystallise the filtrate by heating gently until almost

all of the water evaporates. Do not allow evaporation to dryness.

Questions
1. Which reaction occurred in this experiment? Explain with a balanced
chemical equation.

2. Why was the mixture filtered before evaporation?
3. How can the gas formed in this experiment be tested?

Reactions of acids with metal hydrogencarbonates
Metal hydrogencarbonates, or commonly known as bicarbonates, are compounds
in the form of MHCO , where M represents a metal. These compounds react
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with acids in the same way as metal carbonates to form a salt, water, and carbon
dioxide gas. For example, sodium hydrogencarbonate (NaHCO ) reacts with
3
dilute hydrochloric acid to produce sodium chloride, water, and carbon dioxide gas.

Preparation of salts by direct combination
If salts are required in anhydrous forms, they cannot be prepared by wet methods.
In this case, it is possible to prepare them by direct combination. For example, in
the preparation of iron(III) chloride, dry chlorine gas is passed over hot iron wire
or steel wool as shown in Figure 5.14. The iron(III) chloride vapour produced is
condensed to give a solid salt. This is indicated in the following equation:

Student’s Book Form Two 129

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CHEMISTRY FORM TWO NEW 2025 DUMMY.indd 129