Page 98 - Science Coursebook

7.2 Preparing a salt using metal and acid

In Topic 6.3, you investigated how metals react with dilute acids. This
is often a good way of making a salt.
The general equation for the reaction of metals with acid is:

acid + metal → salt + hydrogen
The equation for the reaction between zinc and hydrochloric acid is:
zinc + hydrochloric acid → zinc chloride + hydrogen

Questions
1 Which of the compounds in the equation above is a salt?
A+I 2 Which acid would you add to the metal magnesium to make
the salt magnesium sulfate?

A+I 3 Write the word equation for the reaction of iron with
hydrochloric acid. Zinc reacting with an acid.
A+I 4 Why would it be dangerous to prepare sodium chloride by
reacting sodium with hydrochloric acid?

Activity 7.2A

Making the salt zinc sulfate

SE Safety: Be careful when heating the evaporating basin (dish) step 3
as the solution may spit and burn you.

3
3
1 Pour about 50 cm of sulfuric acid into a 250 cm beaker.
2 Add zinc metal (1–5 g) to the acid in the beaker.
3 Once the mixture stops fizzing pour it into an

evaporating dish. Heat the evaporating dish very gently
until you see crystals forming at the edge of the solution.
4 Remove from the heat and leave for a few days to
form crystals.

Questions
A1 Write the word equation for this reaction.
A2 What are the important practical points you need to
consider when you evaporate the solution?
A3 Which do you think is the better way to produce large
crystals – heating the evaporating dish until there is
very little liquid left or leaving it to evaporate slowly?

96 7 Salts

A+E SE