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New
Year 10
OCR
Higher

Making a pure dry sample of a soluble salt

I can carry out a multistage chemical procedure to make a pure dry sample of a soluble salt.

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New
New
Year 10
OCR
Higher

Making a pure dry sample of a soluble salt

I can carry out a multistage chemical procedure to make a pure dry sample of a soluble salt.

Download all resources
Share activities with pupils

Lesson details

Key learning points

  1. Reacting a metal oxide with an appropriate acid can form a desired salt and water.
  2. Adding metal oxide to excess ensures that the acid fully reacts to form salt and water.
  3. Excess metal oxide can be removed by filtration so that the filtrate contains only salt and water.
  4. Water can be removed from the salt by evaporation.

Common misconception

Pupils often do not understand that observing excess metal oxide in the reaction mixture means that the acid has fully reacted.

Emphasise how to observe the end of the reaction and what these observations mean, i.e. excess metal oxide in the reaction mixture or using pH paper to indicate the solution is neutral. Both are evidence of the acid having fully reacted.

Keywords

  • Soluble - When a substance dissolves in a liquid, it is described as soluble in that liquid.

  • Excess reactant - any reactant present in a greater amount than is necessary to completely react with the limiting reactant

  • Filtration - a technique to separate insoluble solids from a liquid by passing the mixture it is in through a filter

  • Crystallisation - a process that forms solid crystals from a saturated solution by evaporating the solvent

Multistage experiments can be quite overwhelming for pupils. Break up the experiment into sections. Demo each section separately i.e. neutralisation, filtration and crystallisation and, after each, get the pupils to perform that section.
Teacher tip

Equipment

dilute sulfuric acid, copper oxide, measuring cylinder, Bunsen burner, tripod and gauze, spatula, beakers, universal indicator paper, filter paper and funnel, conical flask and evaporating dish

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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Starter quiz

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6 Questions

Q1.
How can you increase the concentration of a solution?
by adding solvent
by diluting the solution
Correct answer: by adding solute
by decreasing the temperature
Correct answer: by removing solvent
Q2.
What is the purpose of filtration?
to dissolve solids in a liquid
Correct answer: to separate insoluble solids from a liquid
to change the chemical composition of a mixture
to increase the temperature of a mixture
to mix two liquids together
Q3.
Which of the following equations represent neutralisation reactions used for making salts?
Correct answer: metal + acid → salt + hydrogen
Correct answer: metal hydroxide + acid → salt + water
Correct answer: metal oxide + acid → salt + water
Correct answer: metal carbonate + acid → salt + water + carbon dioxide
metal + water → metal hydroxide + hydrogen
Q4.
Match each salt with the reactants that can be used to make it.
Correct Answer:magnesium chloride,magnesium and hydrochloric acid

magnesium and hydrochloric acid

Correct Answer:copper sulfate,copper oxide and sulfuric acid

copper oxide and sulfuric acid

Correct Answer:copper nitrate,copper oxide and nitric acid

copper oxide and nitric acid

Q5.
What is a saturated solution?
a solution that can dissolve more solute
Correct answer: a solution where no more solute can dissolve
a solution that has evaporated completely
a solution mixed with an insoluble solid
a solution that changes colour with more solute
Q6.
What happens during crystallisation?
the solute evaporates leaving the solvent
the solvent dissolves more solute to form crystals
Correct answer: solid crystals form by removing the solvent
the temperature of the solution decreases
the solvent turns into a solid

Exit quiz

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6 Questions

Q1.
Reactions between an acid and a metal, or between an acid and certain metal compounds (like hydroxide, oxide or carbonate), are all types of reactions.
Correct Answer: neutralisation, neutralization
Q2.
An insoluble metal oxide reacts with an acid to make a soluble salt. What are the main steps, in any order, needed to make pure crystals of the soluble salt.
Correct answer: crystallising the soluble salt from a solution
dissolving the metal oxide in water
Correct answer: filtering to remove any excess insoluble metal oxide
Correct answer: neutralising the acid with the insoluble metal oxide
reducing the temperature of the reactant mixture
Q3.
An insoluble metal oxide reacts with an acid to make a soluble salt. Put each step in the correct order to describe how a metal oxide is reacted with an acid, making sure all the acid has reacted.
An image in a quiz
1 - add one spatula at a time of powdered metal oxide to the acid and stir
2 - stop when some of the metal oxide does not react
3 - gently heat the mixture to allow more metal oxide to react with the acid
4 - if needed, add more spatulas of metal oxide until it does not react again
5 - use pH paper to check that the solution is neutral
Q4.
The undissolved impurity in a salt solution that remains in filter paper after filtration is called the .
An image in a quiz
Correct Answer: residue
Q5.
Put each step in the correct order to describe how to obtain crystals of salt from a pure salt solution.
An image in a quiz
1 - light a Bunsen burner and turn the gas tap down to give a small yellow flame
2 - open the air hole to get a small blue flame
3 - use it to gently heat the solution in a evaporating dish over a water bath
4 - remove the Bunsen burner each time the solution bubbles vigorously
5 - replace the Bunsen burner, as necessary, to evaporate more water
6 - stop heating when there is still a little water left
7 - the rest of the water should evaporate as the evaporating dish cools down
Q6.
Match these key terms to the correct definitions.
Correct Answer:soluble,the property of a substance that dissolves in a liquid

the property of a substance that dissolves in a liquid

Correct Answer:excess reactant,the reactant left over after a reaction is complete

the reactant left over after a reaction is complete

Correct Answer:filtration,a technique for separating insoluble solids from a liquid

a technique for separating insoluble solids from a liquid

Correct Answer:crystallisation,forming solid crystals from a saturated solution by evaporation

forming solid crystals from a saturated solution by evaporation

Correct Answer:limiting reactant,the reactant that is fully used up during a reaction

the reactant that is fully used up during a reaction