Practise 21 exam-style questions on Properties of ionic compounds for AQA GCSE Chemistry. Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with an AI tutor on hand if you get stuck.
21 questions
1–6 marks each
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20 questions, marked as you go
Sample questions with model answers
Here are 4 of the questions in this topic, each with a model answer, an explanation of why it earns the marks and the mark scheme an examiner would use.
Question 1
2 marks
The diagram shows the arrangement of ions in solid sodium chloride.
Explain why solid sodium chloride does not conduct electricity.
Model answer
In the solid, the ions are held in fixed positions by strong electrostatic forces. They can only vibrate, so they cannot move through the solid to carry charge.
Explanation
An ionic compound contains charged particles, but to conduct, charged particles must be able to move. In the solid lattice the ions are locked in place, so no charge can flow.
Mark scheme
1 mark
the ions are held in fixed positions (in the lattice)
allow ions can only vibrate
1 mark
so the ions cannot move (through the solid) to carry charge
do not accept 'electrons cannot move' for this mark; ignore 'no delocalised electrons'
Question 2
2 marks
Lithium fluoride melts at 845 °C. Silicon tetrachloride melts at −69 °C. One of these compounds is ionic and the other consists of small molecules.
Identify the ionic compound. Give a reason for your answer.
Model answer
Lithium fluoride is ionic. It has a much higher melting point, because a lot of energy is needed to overcome the strong electrostatic forces between the ions in its giant lattice.
Explanation
Ionic compounds have high melting points; substances made of small molecules usually have low ones. Lithium is a metal and fluorine a non-metal, so lithium fluoride is ionic, whereas silicon and chlorine are both non-metals.
Mark scheme
1 mark
lithium fluoride
1 mark
it has a high melting point (because a lot of energy is needed to overcome the strong electrostatic forces between the ions)
allow it is made from a metal and a non-metal
Question 3
3 marks
Describe what happens to the ions in sodium chloride as it is heated from room temperature until it has completely melted.
Model answer
As the sodium chloride is heated, the ions gain energy and vibrate faster about their fixed positions in the lattice. At the melting point the ions have enough energy to overcome the strong electrostatic forces between them, so the regular lattice breaks down and the ions can move around each other.
Explanation
The ions themselves do not change when sodium chloride melts. Energy is needed to overcome the electrostatic attraction between them, and a lot of energy is needed because these forces are strong.
Mark scheme
1 mark
the ions gain energy and vibrate more / faster (about fixed positions)
1 mark
at the melting point (801 °C) the ions have enough energy to overcome the strong electrostatic forces holding them in the lattice
allow ionic bonds overcome; do not accept intermolecular forces or covalent bonds
1 mark
the ions leave their fixed positions and can move around each other
allow regular arrangement breaks down
Question 4
4 marks
A teacher has two unlabelled white solids. One is sodium chloride and the other is glucose, which is made of covalent molecules.
Describe how a student could use electrical conductivity to identify which solid is sodium chloride. Explain the results the student would get.
Model answer
Dissolve a sample of each solid in distilled water. Dip two electrodes connected in series with a power supply and a bulb (or ammeter) into each solution. The sodium chloride solution will conduct and the bulb will light, because the sodium and chloride ions are free to move and carry charge. The glucose solution will not conduct, because glucose is made of molecules that have no overall electric charge.
Explanation
Testing the solids directly would not work, because neither conducts as a solid. Dissolving frees the ions in sodium chloride, while a molecular substance such as glucose still has no charged particles. Distilled water is used so that the water itself contains no ions.
Mark scheme
1 mark
dissolve each solid in (distilled / deionised) water
allow melt each solid
1 mark
test each solution with two electrodes connected to a power supply and a bulb / ammeter
1 mark
the sodium chloride solution conducts / bulb lights, but the glucose solution does not
1 mark
because sodium chloride contains ions that are free to move in solution, but glucose molecules have no overall charge
allow glucose has no ions
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