Page 133 - Chemistry_Form_2

Chemistry
for Secondary Schools

Preparation of soluble salts

Soluble salts are prepared by reacting acids with metals, alkalis, insoluble bases
or carbonates.

FOR ONLINE READING ONLY
Reactions of acids with metals (displacement method)
The displacement method is suitable for preparing salts of moderately reactive
metals such as zinc, iron, lead, tin, and copper. Highly reactive metals such
as K, Na, and Ca react very rapidly with acids and can cause explosions. The
displacement reaction occurs as shown in the general equation:

For example, zinc displaces hydrogen from sulfuric acid as shown in the following
reaction equation:

Activity 5.7

Aim: To prepare zinc sulfate
Requirements: Beaker, evaporating dish, glass rod, spatula, tripod stand, wire
gauze, filter papers, filter funnel, heat source, zinc granules,
and 1M dilute sulfuric acid
Procedure

1. Put about 25 cm of 1 M dilute sulfuric acid in a beaker, and then add some
3
zinc granules into it. Mix the contents by using a glass rod.
2. Continue adding more zinc to the beaker to excess until no more
effervescence is observed.

3. Filter out the excess zinc and pour the filtrate into an evaporating dish.
4. Heat the filtrate while ensuring that not all the water is evaporated.

5. Allow the heated filtrate to cool and then filter off any excess liquid.
6. Allow the crystals to dry by rubbing them between filter papers. Record

the observations.

Questions
1. Why excess zinc is used in this experiment?

2. Why is it not allowed to dry up completely the filtrate when evaporating?

126 Student’s Book Form Two

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CHEMISTRY FORM TWO NEW 2025 DUMMY.indd 126