Atoms into Ions & Ions into Atoms (AQA GCSE Combined Science: Synergy: Physical Sciences): Exam Questions

Zinc reacts with copper sulfate to produce zinc sulfate and copper.

Complete the word equation for the reaction.

zinc + ------ → ------ + ---------

This question is about electrolysis.

An aqueous solution of copper sulfate was electrolysed.

0.0400 moles of copper were deposited at the negative electrode.

Calculate the number of copper atoms in 0.0400 moles of copper.

Give your answer to 3 significant figures.

Avogadro constant = 6.02 × 10²³ per mole [3 marks]

Number of copper atoms (3 significant figures) =__________________

An aqueous solution of sodium chloride is electrolysed.

Chlorine is produced at the positive electrode.

Hydrogen is produced at the negative electrode.

Write a half equation for the reaction at the positive electrode. [2 marks]

Explain how hydrogen gas is produced at the negative electrode. [4 marks]

Describe the test for hydrogen gas.

Give the result of the test.

[2 marks]

This question is about electrolysis.

Figure 9 shows the electrolysis of molten potassium chloride using inert electrodes.

Figure 9: Apparatus showing molten potassium chloride between two inert electrodes (negative and positive), connected to a power supply.

Why must potassium chloride be molten during the electrolysis?

Why are inert electrodes used in electrolysis?

A gas is released during the electrolysis of molten potassium chloride.

Describe the test to identify the gas released.

Give the result if the gas is present.

Potassium is produced at the negative electrode.

Write the half equation for the reaction at the negative electrode during the electrolysis of molten potassium chloride.

K⁺ + →

An aqueous solution of potassium chloride was electrolysed.

Hydrogen gas was produced at the negative electrode.

Explain why hydrogen gas is produced during the electrolysis of an aqueous solution of potassium chloride.

An aqueous solution of copper chloride is electrolysed using inert electrodes.

What is meant by 'inert'?

Describe the test for hydrogen gas.

Give the result of the test.

What is the result of the test for hydrogen?

A student investigated the reactivity of four metals with sulfuric acid.

Figure 5 shows the apparatus.

Figure 5: Four test tubes containing sulfuric acid, each with a piece of one of the four metals (magnesium, iron, copper, zinc), all bubbling out hydrogen gas.

Give two variables the student should control.

Write the order of reactivity from least reactive to most reactive for the four metals.

Use Figure 5.

Least reactive → ........... → ........... → ........... → Most reactive

The gas produced in Figure 5 is hydrogen.

Describe the test for hydrogen gas.

Give the result if hydrogen is present.

The student repeated the investigation using different apparatus to determine the rate of reaction.

Figure 6 shows part of the apparatus.

Figure 6: A conical flask containing metal with sulfuric acid, and a 100 cm³ measuring cylinder inverted in a trough of water, ready to collect the gas produced. A stopwatch is shown next to the apparatus.

Complete Figure 6 so that the apparatus can be used to determine the rate of reaction.

What is the unit for the rate of reaction determined using the apparatus in Figure 6?

Copper sulfate solution contains copper ions and hydrogen ions.

Why is copper produced instead of hydrogen during the electrolysis of copper sulfate solution?

Tick (✓) one box.

What is the name given to solutions that conduct electricity?

The student electrolyses a solution of potassium chloride.

Figure 1 shows the apparatus she uses (a beaker of potassium chloride solution with two inert electrodes connected to a d.c. power supply; bubbles of gas are produced at each electrode).

When the current is switched on, bubbles of hydrogen gas are given off at the negative electrode.

Explain why hydrogen is produced and not potassium.

The student then compares the relative conductivity of different concentrations of potassium chloride.

Figure 2 shows the apparatus she uses (a beaker of water with two electrodes connected to a conductivity meter; potassium chloride solution is added drop by drop).

This is the method used.

1. Add potassium chloride solution to the water one drop at a time.

2. Stir the mixture.

3. Record the reading on the conductivity meter.

Table 1 shows the student's results.

Table 1

When there is no potassium chloride in the beaker no electrical charge flows.

Suggest why pure water does not conduct electricity.

Describe the relationship shown in Table 1.

This question is about the reactions of acids.

When dilute hydrochloric acid is reacted with sodium hydroxide solution there is a temperature change.

Explain how the temperature changes.

A student reacted four metals with water and with a dilute acid to work out the order of reactivity of the metals.

Table 1 shows some of the observations.

Table 1

Write the observations for X and Y.

Observation at X:

Observation at Y:

Write the four metals, calcium, copper, magnesium and zinc, in order of reactivity.

Start with the most reactive metal.

Some gases given off in reactions can be identified by chemical tests.

Draw one line from each chemical test to the name of the gas.

Chemical tests:

• Put in a lighted splint. The gas burns with a pop sound.

• Put in a glowing splint. The gas relights the splint.

• Put into limewater. The gas turns limewater cloudy.

Gases:

• Carbon dioxide

• Chlorine

• Hydrogen

• Nitrogen

• Oxygen

Iron is a metal that has many uses.

Iron is extracted from iron ore. Part of the process involves reduction of the ore with carbon monoxide.

Iron ore contains iron oxide (Fe₂O₃).

Write a balanced equation for the reaction of iron oxide with carbon monoxide.

This question is about the electrolysis of two compounds.

Figure 9 shows the electrolysis of molten lead bromide (a crucible of molten PbBr₂ with two electrodes connected to a power supply; bubbles of gas form at the positive electrode and molten lead collects at the negative electrode).

The electrolyte contains lead ions (Pb²⁺) and bromide ions (Br⁻).

Complete the sentences. Use words from the box.

Box: atoms, bromide, bromine, ions, lead, molecules, oxygen

At the positive electrode the gas produced is .

At the negative electrode lead gain electrons and turn into lead .

A student measured the volumes of each gas produced during the electrolysis of water.

Table 3 shows the student's results.

Table 3

The student plotted a graph of the results for oxygen. Figure 10 shows the graph.

The student did not put a scale on the y-axis.

On the graph in Figure 10:

• complete the scale for the y-axis

• plot the results for hydrogen

• include a line of best fit.

Use the graph to calculate the mean volume of oxygen produced per second.

Mean volume of oxygen produced = cm³/s