Volumes of gases

This question is about iron.

Iron is a metal.

Describe how iron conducts thermal energy.

Pure iron is too soft for many uses.

Explain why mixing iron with other metals makes alloys which are harder than pure iron.

When iron reacts with chlorine, 0.12 mol of iron reacts with 0.18 mol of chlorine (Cl₂).

Which is the correct equation for the reaction?

Tick () one box.

The most common oxides of iron are Fe₂O₃ and Fe₃O₄

What is the ratio of the numbers of ions in Fe₃O₄?

Tick () one box.

Calculate the percentage (%) by mass of iron in Fe₃O₄

Relative atomic masses (A_r): O = 16 Fe = 56

Fe₂O₃ reacts with carbon to produce carbon dioxide.

The equation for the reaction is:

Calculate the volume of carbon dioxide gas at room temperature and pressure that is produced from 40.0 kg of Fe₂O₃ using excess carbon.

Relative formula mass (M_r): Fe₂O₃ = 160

The volume of 1 mole of any gas at room temperature and pressure is 24 dm³.

This question is about electrolysis.

Aluminium is manufactured by electrolysing a molten mixture of aluminium oxide

Complete the half equation for the reaction occurring at the negative electrode.

Cryolite contains Na⁺ ions as well as Al³⁺ ions. Suggest one reason why sodium is not a product of the electrolysis.

A student investigated the electrolysis of an aqueous solution of a different compound. Figure 7 shows the apparatus.

Hydrogen was produced at the negative electrode and oxygen was produced at the positive electrode.

Explain how oxygen was produced from water during the electrolysis of this aqueous solution.

The student compared the volumes of the two gases collected. How can the student change the apparatus in Figure 7 to compare the volumes of the two gases produced more accurately? Give one reason for your answer.

The overall equation for the reaction is:

What is the volume of oxygen produced when 20 cm³ of hydrogen has been produced?

Tick (✓) one box.

This question is about titanium dioxide (TiO₂).

Self-cleaning windows are coated with a layer of nanoparticles of titanium dioxide. Titanium dioxide:

• helps sunlight break down dirt particles

• attracts water, so dirt is washed away by rain.

Nanoparticles of titanium dioxide are used instead of fine particles of titanium dioxide for coating self-cleaning windows. Suggest two reasons why.

Titanium is extracted from titanium dioxide in a two-stage process. The equation for the first stage in the process is:

Calculate the volume of chlorine gas needed to react completely with 100 kg of titanium dioxide. Relative atomic masses (A_r): O = 16 Ti = 48 The volume of one mole of gas = 24 dm³

This question is about silicon and compounds of silicon.

The reactivity series sometimes includes non-metals such as carbon, hydrogen and silicon. Silicon can be extracted by reducing silicon dioxide with different substances. The equation for one possible reaction is:

Explain what this reaction shows about the position of silicon in the reactivity series.

Aluminium also reduces silicon dioxide. Carbon is used rather than aluminium to reduce silicon dioxide because carbon is cheaper than aluminium. Carbon can be obtained by heating coal. Aluminium is obtained from aluminium oxide. Explain why aluminium is more expensive than carbon.

Magnesium also reduces silicon dioxide. The equation for the reaction is:

Give one reason why the products are difficult to separate if magnesium is used to reduce silicon dioxide.

Calculate the minimum mass in grams of magnesium needed to completely reduce 1.2 kg of silicon dioxide. Relative atomic masses (A_r): O = 16 Mg = 24 Si = 28

Si₂H₆ is a covalent compound of silicon and hydrogen.

Complete Figure 9 to show the outer shell electrons in a molecule of Si₂H₆

Si₂H₆ reacts with oxygen. The equation for the reaction is:

30 cm³ of Si₂H₆ is reacted with 150 cm³ (an excess) of oxygen.

Calculate the total volume of gases present after the reaction. All volumes of gases are measured at the same temperature and pressure.

This question is about salts.

Name the salt produced by the neutralisation of hydrochloric acid with potassium hydroxide.

Write an ionic equation for the neutralisation of hydrochloric acid with potassium hydroxide.

Soluble salts can be produced by reacting dilute hydrochloric acid with an insoluble solid. Copper, copper carbonate and copper oxide are insoluble solids. Which of these insoluble solids can be used to make a copper salt by reacting the solid with dilute hydrochloric acid? Tick (✓) one box.

A student makes crystals of magnesium sulfate. This is the method used.

1. Add sulfuric acid to a beaker.

2. Warm the sulfuric acid.

3. Add a spatula of magnesium oxide to the beaker.

4. Stir the mixture.

5. Repeat steps 3 and 4 until there is magnesium oxide remaining in the beaker.

6. Filter the mixture.

7. Evaporate the filtrate gently until crystals start to form.

8. Leave the solution to finish crystallising.

Give one reason for:

• step 2

• step 5

• step 6.

How should the filtrate be evaporated gently in step 7 ?

Iron chloride is produced by heating iron in chlorine gas. The equation for the reaction is:

Calculate the volume of chlorine needed to react with 14 g of iron. You should calculate:

• the number of moles of iron used

• the number of moles of chlorine that react with 14 g of iron

• the volume of chlorine needed.

Relative atomic mass (A_r): Fe = 56 The volume of 1 mole of gas = 24 dm³

This question is about the reaction between hydrogen sulfide (H₂S) and oxygen. The equation for the reaction is:

What does H₂O(g) represent?

Calculate the volume of oxygen required to react with 50 cm³ of hydrogen sulfide.

Figure 6 shows part of the reaction profile for the reaction. The reaction is exothermic. Complete Figure 6. You should:

• complete the profile line

• label the activation energy

• label the overall energy change.

Figure 7 shows the displayed formula equation for the reaction of hydrogen sulfide with oxygen.

Figure 7

Table 5 shows some of the bond energies.

In the reaction the energy released forming new bonds is 1034 kJ/mol greater than the energy needed to break existing bonds. Calculate the bond energy X for the bond. Use Figure 7 and Table 5.

The reaction between hydrogen and oxygen releases energy.

A student drew a reaction profile for the reaction between hydrogen and oxygen. Figure 3 shows the student’s reaction profile.

The student made two errors when drawing the reaction profile. Describe the two errors.

The reaction between hydrogen and oxygen in a hydrogen fuel cell is used to produce electricity. Hydrogen fuel cells and rechargeable cells are used to power some cars. Give two advantages of using hydrogen fuel cells instead of using rechargeable cells to power cars.

Reactions occur at the positive electrode and at the negative electrode in a hydrogen fuel cell. Write a half equation for one of these reactions.

The three states of matter can be represented by a simple particle model. Figure 4 shows a simple particle model for hydrogen gas.

Give two limitations of this simple particle model for hydrogen gas.

The hydrogen gas needed to power a car for 400 km would occupy a large volume. Suggest one way that this volume can be reduced.

The energy needed for a car powered by a hydrogen fuel cell to travel 100 km is 58 megajoules (MJ). The energy released when 1 mole of hydrogen gas reacts with oxygen is 290 kJ The volume of 1 mole of a gas at room temperature and pressure is 24 dm³ Calculate the volume of hydrogen gas at room temperature and pressure needed for the car to travel 100 km

This question is about electrolysis. Aluminium is produced by electrolysing a molten mixture of aluminium oxide and cryolite.

Explain why a mixture is used as the electrolyte instead of using only aluminium oxide.

What happens at the negative electrode during the production of aluminium? Tick (✓) one box.

Oxygen is produced at the positive electrode. Complete the balanced half-equation for the process at the positive electrode.

Explain why the positive electrode must be continually replaced.

The overall equation for the electrolysis of aluminium oxide is:

Calculate the mass of oxygen produced when 2000 kg of aluminium oxide is completely electrolysed. Relative atomic masses (A_r): O = 16 Al = 27

Sodium metal and chlorine gas are produced by the electrolysis of molten sodium chloride.

Explain why sodium chloride solution cannot be used as the electrolyte to produce sodium metal.

Calculate the volume of 150 kg of chlorine gas at room temperature and pressure. The volume of one mole of any gas at room temperature and pressure is 24.0 dm³ Relative formula mass (M_r): Cl₂ = 71

A student investigated the electrolysis of different substances. Figure 6 shows the apparatus.

Explain why electrolysis would not take place in the apparatus shown in Figure 6.

Explain why graphite conducts electricity. Answer in terms of the structure and bonding in graphite.

The student investigated how the volume of gases produced changes with time in the electrolysis of sodium chloride solution. Figure 7 shows the apparatus.

The student made an error in selecting the apparatus for this investigation. How should the apparatus be changed? Give one reason for your answer.

Another student used the correct apparatus. This student measured the volumes of gases collected every minute for 20 minutes. Figure 8 shows the student’s results.

Describe the trends shown in the results. Use values from Figure 8.

The number of moles of each gas produced at the electrodes is the same. No gas escapes from the apparatus. Suggest one reason for the difference in volume of each gas collected.

Calculate the amount in moles of chlorine collected after 20 minutes. Use Figure 8. The volume of one mole of any gas at room temperature and pressure is 24.0 dm³ Give your answer in standard form.