Amounts of substance in equations

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 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 the halogens. Table 5 shows the melting points and boiling points of some halogens.

What is the state of bromine at 0 °C and at 100 °C? Tick (✓) one box. State at 0 °C State at 100 °C

Explain the trend in boiling points of the halogens shown in Table 5.

Why is it not correct to say that the boiling point of a single bromine molecule is 59 °C?

Iron reacts with each of the halogens in their gaseous form. Figure 5 shows the apparatus used.

Give one reason why this experiment should be done in a fume cupboard.

Explain why the reactivity of the halogens decreases going down the group.

A teacher investigated the reaction of iron with chlorine using the apparatus in Figure 5. The word equation for the reaction is: iron + chlorine → iron chloride The teacher weighed:

• the glass tube

• the glass tube and iron before the reaction

• the glass tube and iron chloride after the reaction.

Table 6 shows the teacher’s results.

Calculate the simplest whole number ratio of: moles of iron atoms moles of chlorine atoms Determine the balanced equation for the reaction. Relative atomic masses (A_r): Cl = 35.5 Fe = 56

Equation for the reaction

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

Copper forms two oxides, Cu₂O and CuO A teacher investigated an oxide of copper. Figure 10 shows the apparatus.

This is the method used.

1. Weigh empty tube A.

2. Add some of the oxide of copper to tube A.

3. Weigh tube A and the oxide of copper.

4. Weigh tube B and drying agent.

5. Pass hydrogen through the apparatus and light the flame at the end.

6. Heat tube A for 2 minutes.

7. Reweigh tube A and contents.

8. Repeat steps 5 to 7 until the mass no longer changes.

9. Reweigh tube B and contents.

10. Repeat steps 1 to 9 with different masses of the oxide of copper.

Suggest one reason why step 8 is needed.

Explain why the excess hydrogen must be burned off.

Figure 10 is repeated here.

Table 5 shows the teacher’s results.

When an oxide of copper is heated in a stream of hydrogen, the word equation for the reaction is: copper oxide + hydrogen → copper + water

Determine the mass of copper and the mass of water produced in this experiment. Use Table 5.

The teacher repeated the experiment with a different sample of the oxide of copper. The teacher found that the oxide of copper produced 2.54 g of copper and 0.72 g of water. Two possible equations for the reaction are:

Determine which is the correct equation for the reaction in the teacher’s experiment. Relative atomic masses (A_r): H = 1 O = 16 Cu = 63.5