Conservation of mass & balanced equations

This question is about elements and compounds.

What is the name of the compound with the formula ZnBr₂?

Use the periodic table.

Tick () one box.

A compound has the formula C₂H₆O

Table 1 shows information about a molecule of C₂H₆O

Complete Table 1.

Use the periodic table.

Potassium and sulfur react to produce potassium sulfide.

Write the word equation for this reaction.

Aluminium reacts with fluorine to produce aluminium fluoride.

Balance the equation for this reaction.

This question is about metals and metal oxides.

Tin (Sn) is extracted from tin oxide using carbon.

The equation for the reaction is:

Which substance is reduced in this reaction?

Give one reason for your answer.

Answer in terms of oxygen.

Substance reduced

Why can carbon be used to extract tin from tin oxide?

Cadmium (Cd) can be extracted by the reaction of cadmium oxide with carbon.

The equation for the reaction is:

Calculate the percentage atom economy for the production of cadmium in this reaction.

Relative atomic masses (A_r): C = 12 Cd = 112

Relative formula mass (M_r): CdO = 128

Tungsten is a transition metal.

Potassium is a Group 1 metal.

Give two differences between the properties of tungsten and the properties of potassium.

Tungsten oxide reacts with hydrogen to give tungsten (W) and water.

The equation for the reaction is:

The law of conservation of mass states:

‘The mass of the products equals the mass of the reactants during a chemical reaction.’

Show that the equation obeys the law of conservation of mass.

Relative atomic mass (A_r): W = 184

Relative formula masses (M_r): H₂ = 2 WO₃ = 232 H₂O = 18

The reaction producing tungsten has a high atom economy.

Why is it important to use reactions with a high atom economy in industry?

This question is about metals and metal oxides.

Tin (Sn) is extracted from tin oxide using carbon.

The equation for the reaction is:

Which substance is reduced in this reaction?

Give one reason for your answer.

Answer in terms of oxygen.

Substance reduced

Why can carbon be used to extract tin from tin oxide?

Cadmium (Cd) can be extracted by the reaction of cadmium oxide with carbon.

The equation for the reaction is:

Calculate the percentage atom economy for the production of cadmium in this reaction.

Relative atomic masses (A_r): C = 12 Cd = 112

Relative formula mass (M_r): CdO = 128

Tungsten is a transition metal.

Potassium is a Group 1 metal.

Give two differences between the properties of tungsten and the properties of potassium.

Tungsten oxide reacts with hydrogen to give tungsten (W) and water.

The equation for the reaction is:

The law of conservation of mass states:

‘The mass of the products equals the mass of the reactants during a chemical reaction.’

Show that the equation obeys the law of conservation of mass.

Relative atomic mass (A_r): W = 184

Relative formula masses (M_r): H₂ = 2 WO₃ = 232 H₂O = 18

The reaction producing tungsten has a high atom economy.

Why is it important to use reactions with a high atom economy in industry?

This question is about electrolysis and the extraction of metals.

Why can some molten substances be electrolysed?

Tick () one box.

Table 3 shows the products of the electrolysis of some molten compounds.

Complete Table 3.

Aluminium is extracted by electrolysing molten aluminium oxide.

Balance the equation for the reaction.

Choose numbers from the box.

Calculate the relative formula mass (M_r) of aluminium oxide (Al₂O₃).

Relative atomic masses (A_r): O = 16 Al = 27

Figure 13 shows part of the reactivity series of metals.

The non-metal carbon has been included.

Metals can be extracted from their compounds by:

electrolysis

reduction with carbon.

Electrolysis is more expensive than reduction with carbon.

Predict one metal that would be extracted by each method.

Use Figure 13.

This question is about displacement reactions.

Iron is extracted from iron oxide by a displacement reaction with carbon.

Balance the equation for the reaction.

Iron oxide is reduced in this reaction. How does the equation show that iron oxide is reduced?

Calculate the relative formula mass (M_r) of Fe₂O₃ Relative atomic masses (A_r): O = 16 Fe = 56

Copper oxide reacts with hydrogen to produce copper. The equation for the reaction is:

Calculate the percentage atom economy for obtaining copper from this reaction. Use the equation:

Relative atomic mass (A_r): Cu = 63.5 Relative formula masses (M_r): H₂ = 2 CuO = 79.5

A student investigated the reactivity of four different metals, A, B, C and D. The student:

• added each metal to aqueous solutions of each of the metal sulfates

• observed whether a reaction took place.

Give one observation that would show a reaction took place.

Table 4 shows the results.

shows that a displacement reaction took place. × shows that a displacement reaction did not take place. Write metals A, B, C and D in order of reactivity. Give a reason for your order of reactivity.

This question is about elements in the periodic table.

Argon has the atomic number 18 Explain why argon does not form compounds. Answer in terms of electrons.

Phosphorus (P) is the element below nitrogen in the periodic table. Predict the formula of the compound formed between phosphorus and hydrogen.

Tellurium is the element with atomic number 52 Predict whether tellurium reacts with metals. Explain your answer. Answer in terms of the position of tellurium in the periodic table.

Barium (Ba) is an element in Group 2 of the periodic table. Barium reacts with hydrochloric acid.

Suggest two observations that could be made when barium reacts with hydrochloric acid.

Write a balanced symbol equation for the reaction between barium and hydrochloric acid.

This question is about acids and alkalis.

Which ion do acids produce in aqueous solution?

Tick (✓) one box.

Acids react with alkalis.

What is the name of this type of reaction?

Tick (✓) one box.

Balance the equation for the reaction between sulfuric acid and potassium hydroxide.

Universal indicator turns purple in potassium hydroxide solution.

What is the pH of the solution?

Tick (✓) one box.

A student does a titration to find the volume of sulfuric acid that reacts with 25 cm³ of potassium hydroxide solution.

Figure 7 shows the equipment used.

The 25 cm³ of potassium hydroxide solution is measured with the measuring cylinder.

Which piece of equipment could the student use to measure the 25 cm³ of potassium hydroxide solution more accurately?

Tick (✓) one box.

Describe how the student would use the equipment in Figure 7 to complete the titration.

This question is about the elements in Group 7 of the periodic table. Table 1 shows the melting points and boiling points of some of the elements.

What is the state of bromine at 100 °C? Use Table 1. Tick (✓) one box.

What temperature does chlorine gas condense at to form a liquid? Use Table 1.

Complete the sentences.

This is because the size of the molecules increases so the

A teacher investigated the reaction of iron with chlorine. Figure 1 shows the apparatus used.

Why did the teacher do the investigation in a fume cupboard? Tick (✓) one box.

The word equation for the reaction is: iron + chlorine → iron chloride Iron chloride is a solid. The teacher weighed the glass tube and contents:

• before the reaction

• after the reaction.

What happened to the mass of the glass tube and contents during the reaction? Give one reason for your answer.

The mass of the glass tube and contents.

The teacher repeated the investigation with bromine gas and with iodine gas. Table 2 shows the results.

Fluorine is above chlorine in Group 7. Predict what you would observe when fluorine gas reacts with iron. Use Table 2.

Balance the equation for the reaction between iron and bromine.

2 Fe + _____ Br 2 → 2 FeBr 3

Calculate the relative formula mass (M_r) of FeBr₃ Relative atomic masses (A_r): Fe = 56 Br = 80

This question is about silver iodide. Silver iodide is produced in the reaction between silver nitrate solution and sodium iodide solution. The equation for the reaction is: AgNO₃(aq) + NaI(aq) → AgI(s) + NaNO₃(aq)

A student investigated the law of conservation of mass. This is the method used.

1. Pour silver nitrate solution into a beaker labelled A.

2. Pour sodium iodide solution into a beaker labelled B.

3. Measure the masses of both beakers and their contents.

4. Pour the solution from beaker B into beaker A.

5. Measure the masses of both beakers and their contents again.

Table 7 shows the student’s results.

Explain how the results demonstrate the law of conservation of mass. You should use data from Table 7 in your answer.

Suggest how the student could separate the insoluble silver iodide from the mixture at the end of the reaction.

The student purified the separated silver iodide. This is the method used.

1. Rinse the silver iodide with distilled water.

2. Warm the silver iodide.

Suggest one impurity that was removed by rinsing with water.

Suggest why the student warmed the silver iodide.

Calculate the percentage atom economy for the production of silver iodide in this reaction. The equation for the reaction is: AgNO₃(aq) + NaI(aq) → AgI(s) + NaNO₃(aq) Give your answer to 3 significant figures. Relative formula masses (M_r): AgNO₃ = 170 NaI = 150 AgI = 235 NaNO₃ = 85

Give one reason why reactions with a high atom economy are used in industry.

This question is about silver iodide. Silver iodide is produced in the reaction between silver nitrate solution and sodium iodide solution. The equation for the reaction is: AgNO₃(aq) + NaI(aq) → AgI(s) + NaNO₃(aq)

A student investigated the law of conservation of mass. This is the method used.

1. Pour silver nitrate solution into a beaker labelled A.

2. Pour sodium iodide solution into a beaker labelled B.

3. Measure the masses of both beakers and their contents.

4. Pour the solution from beaker B into beaker A.

5. Measure the masses of both beakers and their contents again.

Table 3 shows the student’s results.

Explain how the results demonstrate the law of conservation of mass. You should use data from Table 3 in your answer.

Suggest how the student could separate the insoluble silver iodide from the mixture at the end of the reaction.

The student purified the separated silver iodide. This is the method used.

1. Rinse the silver iodide with distilled water.

2. Warm the silver iodide.

Suggest one impurity that was removed by rinsing with water.

Suggest why the student warmed the silver iodide.

Calculate the percentage atom economy for the production of silver iodide in this reaction. The equation for the reaction is: AgNO₃(aq) + NaI(aq) → AgI(s) + NaNO₃(aq) Give your answer to 3 significant figures. Relative formula masses (M_r): AgNO₃ = 170 NaI = 150 AgI = 235 NaNO₃ = 85

Give one reason why reactions with a high atom economy are used in industry.

A student investigated the reaction between lumps of calcium carbonate and dilute hydrochloric acid. This is the method used.

1. Pour 100 cm³ of dilute hydrochloric acid into a conical flask.

2. Place the conical flask on a balance.

3. Add 2 g of calcium carbonate lumps to the conical flask.

4. Wait until the calcium carbonate stops reacting.

5. Record the decrease in mass of the conical flask and contents.

6. Repeat steps 1 to 5 three more times.

The equation for the reaction is:

What is the state symbol X in the equation? Tick (✓) one box.

Table 2 shows the student’s results.

Why does the mass of the conical flask and contents decrease during the reaction? Tick (✓) one box.

What is the range of the four results in Table 2 ?

Calculate the mean decrease in mass of the conical flask and contents. Do not include the anomalous result. Use Table 2.

A teacher demonstrated the investigation. The teacher used different masses of calcium carbonate. Figure 8 shows the teacher’s results.

What type of variable is the mass of calcium carbonate? Tick (✓) one box.

Use Figure 8 to answer Questions 05.6 and 05.7

Complete the sentence. As the mass of calcium carbonate used increases, the decrease in mass of

What is the decrease in mass of the conical flask and contents when a 3 g sample of calcium carbonate is used?

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

A student investigated the mass of copper oxide produced by heating copper carbonate.

This is the method used.

1. Weigh an empty test tube.

2. Weigh 2.00 g of copper carbonate into the test tube.

3. Heat the copper carbonate until there appears to be no further change.

4. Re-weigh the test tube and copper oxide produced.

5. Subtract the mass of the empty tube to find the mass of copper oxide.

6. Repeat steps 1–5 twice.

7. Repeat steps 1–6 with different masses of copper carbonate.

Table 4 shows the student’s results.

The equation for the reaction is:

Complete the sentence.

Why do the contents of the test tube lose mass in the investigation?

Calculate the mean mass X in Table 4.

One of the results in Table 4 is anomalous.

Which result is anomalous?

Determine the mass of magnesium oxide produced by 8.4 g of magnesium carbonate.

Use Figure 8.

Calculate the mass of magnesium oxide produced when 168 g of magnesium carbonate is heated.

Use your answer to Question 05.7