Oxidation & reduction in terms of electrons

This question is about metals and metal compounds.

A teacher demonstrated the reaction of copper with silver nitrate.

Figure 6 shows the apparatus:

at the start

after a few minutes.

The word equation for the reaction is:

copper + silver nitrate copper nitrate + silver

Silver ions are reduced to silver atoms in the reaction.

What is meant by ‘reduced’ in this reaction?

Complete the ionic equation for the reaction between copper and silver nitrate solution.

You should balance the equation.

Copper nitrate is made up of Cu²⁺ ions and NO₃⁻ ions.

What is the formula of copper nitrate?

Tick () one box.

CuNO₃

Cu(NO₃)₂

Cu₂NO₃

Cu₂(NO₃)₃

Figure 7 shows the order of reactivity for three metals.

Table 2 shows the colours of three metal nitrate solutions.

The teacher added an excess of each metal to each metal nitrate solution.

Complete Table 3 to show the colours of the resultant solutions.

Copper is a good conductor of electricity.

Explain how copper conducts electricity.

Pure copper is too soft for many uses.

Copper is mixed with other metals to make copper alloys.

Explain why copper alloys are harder than pure copper.

This question is about electrolysis.

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

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.

What type of reaction occurs at the negative electrode?

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.

50 cm³ of potassium chloride solution contains 0.030 moles of potassium chloride.

Calculate the concentration of the potassium chloride solution in g/dm³.

Relative formula mass (M_r) of potassium chloride = 74.5

Concentration = g/dm³ _________________

This question is about the extraction of metals.

Name the process that uses bacteria to extract metals.

Iron can be extracted from iron oxide using carbon.

The word equation for the reaction is:

iron oxide + carbon → iron + carbon dioxide

Explain why this reaction is both oxidation and reduction.

Give one reason why some metals cannot be extracted from their oxides using carbon.

Aluminium is manufactured by the electrolysis of a molten mixture of aluminium oxide and cryolite.

Explain why cryolite is used.

Aluminium is produced at the negative electrode.

Complete the half equation for the reaction.

You should balance the equation.

Al³⁺ + ____________ → ____________

This question is about acids and alkalis.

Magnesium reacts with acids to produce a salt and hydrogen.

The ionic equation for the reaction is:

In a redox reaction, both oxidation and reduction occur.

Explain why this reaction is described as a redox reaction.

What happens to the pH of an acid when the hydrogen ion concentration decreases by a factor of ten?

Tick (✓) one box.

The pH decreases by 1.

The pH decreases by 10.

The pH increases by 1.

The pH increases by 10.

Write the ionic equation that represents the neutralisation reaction between an acid and an alkali in aqueous solution.

You should include state symbols.

A teacher demonstrates the reaction of potassium with water.

Give two observations seen when potassium reacts with water.

Potassium reacts with water to form a solution with a pH of 13.

Explain why the solution has a pH of 13.

You should refer to ions in your answer.

Figure 12 shows four models representing the same volume of:

a strong acid at two different concentrations

a weak acid at two different concentrations.

Which model represents the weak acid with the higher concentration?

Tick (✓) one box.

W X Y Z

Justify your answer.

Give two limitations of using the models in Figure 12 to represent acids.

Magnesium and hydrochloric acid react to produce magnesium chloride and hydrogen.

Give the test for hydrogen gas.

Give the result of the test if hydrogen gas is present.

During the reaction between magnesium and hydrochloric acid, hydrogen ions form hydrogen molecules.

The half equation for this process is:

What type of reaction does this half equation show?

Give the reason for your answer.

0.72 g of magnesium reacted completely with dilute hydrochloric acid.

The equation for the reaction is:

Calculate the mass of magnesium chloride produced.

Relative atomic masses (A_r): Mg = 24 Cl = 35.5

A student investigated the electrolysis of potassium chloride solution.

Figure 10 shows the apparatus used.

Why are inert electrodes used?

The student measured the volume of gas collected at each electrode for 25 minutes.

Figure 11 shows the results.

Compare the rate of collection of hydrogen and of chlorine.

Give one similarity and one difference in the rate of collection of the gases.

The rate of production of hydrogen and of chlorine at the electrodes is the same.

Explain how the graph on Figure 11 shows that chlorine is more soluble than hydrogen.

Explain why hydrogen gas is produced at the negative electrode in the electrolysis of potassium chloride solution.

Write the half equation for the production of chlorine gas at the positive electrode.

A teacher demonstrated the extraction of copper from copper oxide.

This is the method used.

1. Mix 1.30 g of zinc and 1.59 g of copper oxide.

2. Heat the mixture strongly.

3. When the mixture starts to glow, stop heating.

4. Let the glow spread through the mixture.

5. Leave the mixture to cool.

6. Add hydrochloric acid to the cooled mixture.

7. Filter the mixture obtained in step 6.

A student concluded that an exothermic reaction had taken place.

Explain how an observation made during the demonstration shows this.

The equation for the reaction between zinc and copper oxide is:

1.59 g of copper oxide reacted.

Calculate the mass of copper produced.

Relative atomic masses (A_r): Cu = 63.5 O = 16 Zn = 65

Explain why steps 6 and 7 result in only copper being obtained as the residue.

The ionic equation for the reaction is:

Which statement about the reaction between zinc and copper ions is correct?

Tick one box.