Conservation of mass & balanced equations

A student investigated the reaction of magnesium with oxygen.

Figure 6 shows the apparatus.

This is the method used.

1. Measure the mass of an empty crucible.

2. Add 0.10 g of magnesium to the crucible.

3. Heat the crucible and contents for 5 minutes.

4. Allow to cool and measure the mass of the crucible and contents.

5. Repeat steps 1 to 4 using different masses of magnesium.

Complete the word equation for the reaction.

magnesium + oxygen →

Complete the sentence.

Choose the answer from the box.

Table 3 shows the measurements for one of the experiments.

Calculate the mass of magnesium in the crucible before heating.

Why does the reaction result in an increase in the mass of the contents of the crucible?

Tick () one box.

The student determined the mass of the contents of the crucible after heating each mass of magnesium.

Figure 7 shows the results.

Draw a ring around the anomalous result in Figure 7.

The student did the experiment using 0.60 g of magnesium four times.

Table 4 shows the results.

Calculate mean value X.

The student used a Bunsen burner instead of a water bath to heat the crucible.

Why did the student use a Bunsen burner?

Tick () one box.

A different student did the investigation.

The student heated the crucible for 1 minute instead of for 5 minutes.

The student obtained different results.

Suggest one reason why the student obtained different results.

Some reactions appear to involve a change in mass.

A student investigated the change in mass when solids were heated.

Figure 7 shows the apparatus.

The student determined the mass of the contents of the crucible at regular intervals.

The student used a Bunsen burner instead of a water bath to heat the crucible.

Suggest one reason why.

The student planned to heat:

• 0.01 mol of magnesium

• 0.01 mol of magnesium carbonate.

The equations for the reactions are:

Figure 8 shows the student’s predicted results.

Look at Figure 8.

Explain the two trends for the first 3 minutes.

Magnesium carbonate

Figure 8 shows that both reactions are complete after 5 minutes.

Why is the final mass of the contents of the crucible the same for both reactions?

The student heated magnesium carbonate.

Figure 9 shows the results.

The student concluded:

‘The difference between the predicted results and the actual results is caused by solid escaping from the crucible.’

Give one reason why the results show the student is not correct.

Iron reacts with steam (H₂O) to produce an oxide of iron and hydrogen gas.

0.120 moles of iron reacts with 0.160 moles of steam.

Determine the balanced equation for the reaction.

You should determine:

• the simplest whole number mole ratio of Fe: H₂O

• the formula of the iron oxide produced.

Balanced equation for the reaction:

Magnesium chloride is a soluble salt.

Magnesium reacts with hydrochloric acid to produce magnesium chloride and a gas.

Which gas is produced?

Tick () one box.

Magnesium chloride (MgCl₂) can be electrolysed when molten.

Tick () one box.

Magnesium chloride contains Mg²⁺ ions and Cl^– ions.

Name the product at each electrode when molten magnesium chloride is electrolysed.

A student investigated the reactivity of three metals: copper, magnesium and iron.

The student mixed each metal with each metal chloride solution.

Table 6 shows the results.

What is the order of reactivity for copper, magnesium and iron?

Give two reasons for your answer.

Use Table 6.

When heated 0.72 g of magnesium reacts with iron oxide to produce 2.32 g of products.

Calculate the mass of iron oxide that reacts with 0.72 g of magnesium.

A student prepared copper sulfate by reacting an acid with excess copper carbonate.

Figure 13 shows the first two stages in the preparation of copper sulfate.

What is the formula of the acid used to prepare copper sulfate?

Tick () one box.

Beaker N contained copper sulfate solution.

Describe how the student could produce copper sulfate crystals from the copper sulfate solution in beaker N.

A student investigated the thermal decomposition of copper carbonate.

Copper carbonate decomposes to form two products.

Figure 14 shows the apparatus.

This is the method used.

1. Add 1.2 g of copper carbonate to a test tube.

2. Heat the test tube and contents until the mass does not change.

3. Record the mass of the contents of the test tube after heating.

4. Repeat steps 1 to 3 with different masses of copper carbonate.

Table 7 shows the results.

Plot the data from Table 7 on Figure 15.

Draw a line of best fit.

Why does the mass of the contents of the test tube decrease in mass when copper carbonate is thermally decomposed?

A student prepared copper sulfate by reacting an acid with excess copper carbonate.

Figure 3 shows the first two stages in the preparation of copper sulfate.

What is the formula of the acid used to prepare copper sulfate?

Tick () one box.

Beaker N contained copper sulfate solution.

Describe how the student could produce copper sulfate crystals from the copper sulfate solution in beaker N.

A student investigated the thermal decomposition of copper carbonate.

Copper carbonate decomposes to form two products.

Figure 4 shows the apparatus.

This is the method used.

1. Add 1.2 g of copper carbonate to a test tube.

2. Heat the test tube and contents until the mass does not change.

3. Record the mass of the contents of the test tube after heating.

4. Repeat steps 1 to 3 with different masses of copper carbonate.

Table 1 shows the results.

Plot the data from Table 1 on Figure 5.

Draw a line of best fit.

Why does the mass of the contents of the test tube decrease in mass when copper carbonate is thermally decomposed?

This question is about extraction of metals.

Aluminium is extracted from a molten mixture of aluminium oxide and cryolite using electrolysis. Figure 12 shows the electrolysis cell.

Complete the sentence.

The extraction of aluminium is expensive because the process uses

Oxygen is produced at the positive carbon electrodes. The oxygen reacts with the carbon electrodes. Which gas is produced when oxygen reacts with the positive carbon electrodes?

Titanium is extracted from titanium chloride by reacting titanium chloride with sodium.

The reaction between titanium chloride and sodium is carried out in an

Suggest why the reaction is carried out in an inert atmosphere.

Complete the sentence. Choose the answer from the box.

Balance the equation for the reaction.

Copper is extracted from copper oxide by reacting copper oxide with carbon.

Figure 13 shows the apparatus.

The equation for the reaction is:

In an experiment 15.9 g of copper oxide and 1.2 g of carbon reacted. 12.7 g of copper was produced in the reaction.

Calculate the mass of carbon dioxide produced in this experiment.

Explain why the mass of the contents in the crucible changed during the experiment.

What happens to copper oxide in the reaction? Give one reason for your answer. Use the equation for the reaction. Tick (✓) one box.

Sodium is in Group 1 of the periodic table. Sodium reacts with oxygen to produce sodium oxide.

Balance the equation for the reaction.

Explain what happens to sodium atoms and to oxygen atoms when sodium reacts with oxygen to produce sodium oxide (Na₂O). Answer in terms of electrons.

Sodium burns in a gas jar of oxygen. Figure 3 shows the apparatus.

Give two observations seen during the reaction.

Describe two differences in the observations if potassium is used instead of sodium.

This question is about hydrogen chloride and sodium hydroxide.

A chlorine atom has 7 electrons in the outer shell. A hydrogen atom has 1 electron in the outer shell. Figure 4 represents part of a dot and cross diagram for a molecule of hydrogen chloride.

Complete the dot and cross diagram. Use dots (ο) and crosses (x) to represent electrons. You should show only the electrons in the outer shells.

Hydrogen chloride dissolves in water to produce hydrochloric acid. Hydrochloric acid reacts with sodium hydroxide solution. Complete the word equation for the reaction between hydrochloric acid and sodium hydroxide.

hydrochloric acid + sodium hydroxide → + water

Solutions of hydrochloric acid and sodium hydroxide are reacted and the temperature change is recorded.

In the reaction, 3.65 g of hydrogen chloride reacts with 4.00 g of sodium hydroxide. 1.80 g of water is produced. Calculate the mass of the other product.

Figure 5 shows part of the thermometer used to measure the temperature.

What is the temperature reading on the thermometer?

In the reaction, the temperature increases. What type of reaction is happening when the temperature increases?

Sodium hydroxide is an alkali. Which two ions are in sodium hydroxide solution? Tick (✓) two boxes.

This question is about elements and compounds.

Magnesium and oxygen react to produce magnesium oxide. Balance the equation for the reaction.

Suggest one safety precaution that should be taken when heating magnesium and oxygen.

Calculate the relative formula mass (M_r) of magnesium fluoride (MgF₂). Relative atomic masses (A_r): F = 19 Mg = 24

Argon is a noble gas. Explain why no product is formed when magnesium and argon are heated together.

Figure 10 shows a reactivity series.

Figure 10

Draw one line from each metal to the method used to extract that metal. Use Figure 10.

Metal Method used to extract that metal

A substance conducts electricity when it has charged particles that are free to move.

Figure 11 represents the structure of sodium chloride.

Explain why sodium chloride conducts electricity when molten but not when solid.

Figure 12 represents the structure of sodium metal.

Explain why sodium metal conducts electricity when solid.

This question is about elements and compounds.

Figure 8 shows a reactivity series.

Figure 8

Give the method and conditions used to extract metal Y from a compound of metal Y

Sodium reacts with titanium chloride (TiCl₄) to produce titanium.

Complete the equation. You should balance the equation.

The reaction between sodium and titanium chloride is a redox reaction. Write a half-equation to show that sodium is oxidised in this reaction.

108 g of aluminum reacts with 1.21 kg of copper chloride to produce copper. The equation for the reaction is:

Calculate the maximum mass of copper produced in grams (g). You should determine the limiting reactant. Relative atomic masses (A_r): Al = 27 Cu = 63.5 Relative formula masses (M_r): CuCl₂ = 134.5 AlCl₃ = 133.5

Limiting reactant is Mass of copper = g

Sodium metal and sodium chloride are both able to conduct electricity.

Describe how sodium metal conducts electricity.

Explain how sodium chloride can conduct electricity.

Magnesium is in Group 2 of the periodic table. 1.0 g of magnesium reacted with chlorine to produce magnesium chloride.

Which types of element react when magnesium reacted with chlorine? Tick (✓) one box.

Write the word equation for the reaction when magnesium reacts with chlorine.

What apparatus was used to measure the mass of 1.0 g of magnesium? Tick (✓) one box.

What mass of magnesium chloride was produced? Tick (✓) one box.

Magnesium reacts with oxygen to produce magnesium oxide. Calculate the percentage mass of magnesium in magnesium oxide (MgO). Relative atomic mass (A_r): Mg = 24 Relative formula mass (M_r): MgO = 40

Magnesium carbonate decomposes to produce magnesium oxide and carbon dioxide.

The word equation for the reaction is: magnesium carbonate → magnesium oxide + carbon dioxide Four students heated 2.00 g of magnesium carbonate for 10 minutes. Table 1 shows the results.

What is the most likely reason for Student 3 ’s anomalous result? Tick (✓) one box.

Calculate value X in Table 1. Do not use the anomalous result. Give your answer to 2 significant figures.

Sodium and potassium are Group 1 elements.

What is the name of Group 1 elements? Tick (✓) one box.

Figure 5 represents the melting points of Group 1 elements.

What is the melting point of sodium?

Sodium reacts with water to produce sodium hydroxide and hydrogen. Balance the equation for the reaction.

Calculate the relative formula mass (M_r) of sodium hydroxide (NaOH). Relative atomic masses (A_r): H = 1 O = 16 Na = 23

Sodium and potassium both react with water. Figure 6 shows sodium reacting with water.

Compare what is seen when sodium reacts with water and when potassium reacts with water.

Metal oxides are produced when metals are heated in air. A student investigated the change in mass when 0.12 g of magnesium was heated in air. Figure 5 shows the apparatus.

The student measured the mass of magnesium oxide produced.

0.12 g of magnesium reacted to produce 0.20 g of magnesium oxide. Calculate the number of moles of oxygen gas (O₂) that reacted. Relative atomic mass (A_r): O = 16

The student repeated the experiment without a lid on the crucible. Suggest why the mass of magnesium oxide produced would be different without a lid on the crucible.

Copper reacts with oxygen to produce copper oxide. 63.5 g of copper produces 79.5 g of copper oxide. Calculate the mass of copper oxide produced when 0.50 g of copper reacts with oxygen. Give your answer to 3 significant figures.

Iron reacts with oxygen to produce an oxide of iron. 0.015 moles of iron reacts with 0.010 moles of oxygen gas (O₂). Determine:

• the formula of the iron oxide produced

• the balanced symbol equation for the reaction.

Balanced symbol equation

This question is about gold and compounds of gold. In the alpha particle scattering experiment alpha particles are fired at gold foil. Alpha particles are positively charged. Figure 4 shows the results.

Some alpha particles are deflected. Complete the sentence. Choose the answer from the box.

Some alpha particles are deflected because the nucleus of the atom is.

Why are most alpha particles not deflected? Tick (✓) one box.

What was one conclusion from the alpha particle scattering experiment? Tick (✓) one box.

Gold reacts with the elements in Group 7 of the periodic table.

What are Group 7 elements known as? Tick (✓) one box.

Fluorine, chlorine and bromine react with gold. Which element will be the most reactive with gold?

Tick (✓) one box.

3.94 g of gold reacts with chlorine to produce 6.07 g of gold chloride. The word equation for the reaction is: gold + chlorine → gold chloride Calculate the mass of chlorine that reacts with 3.94 g of gold.

Calculate the relative formula mass (M_r) of gold chloride (AuCl₃). Relative atomic masses (A_r): Cl = 35.5 Au = 197

This question is about elements and compounds.

Figure 5 shows the proportion of elements in the periodic table that are metals and non-metals.

Determine the percentage of the elements in Figure 5 that are metals.

Give two physical properties of metals.

Sodium reacts with chlorine to produce sodium chloride. Balance the equation for the reaction.

Figure 6 shows part of the structure of sodium chloride (NaC l).

What holds the particles together in sodium chloride? Use Figure 6. Tick (✓) one box.

Solid sodium chloride does not conduct electricity. Give two ways in which sodium chloride can be made to conduct electricity.

Some students investigated the thermal decomposition of metal carbonates. The word equation for the reaction is: metal carbonate → metal oxide + carbon dioxide The students made the following hypothesis: ‘When heated the same mass of any metal carbonate produces the same mass of carbon dioxide.’

The students heated a test tube containing copper carbonate. Table 4 shows their results.

Plan a method the students could use to test their hypothesis. You should show how the students use their results to test the hypothesis. You do not need to write about safety precautions.

Some students investigated the thermal decomposition of metal carbonates. The word equation for the reaction is: metal carbonate → metal oxide + carbon dioxide The students made the following hypothesis: ‘When heated the same mass of any metal carbonate produces the same mass of carbon dioxide.’

The students heated a test tube containing copper carbonate. Table 1 shows their results.

Plan a method the students could use to test their hypothesis. You should show how the students use their results to test the hypothesis. You do not need to write about safety precautions.

This question is about Group 1 elements.

Sodium reacts with chlorine to produce sodium chloride. Balance the equation for the reaction.

4.6 g of sodium reacts with chlorine to produce 11.7 g of sodium chloride. What mass of chlorine reacted?

A teacher puts hot sodium into a gas jar of chlorine. The changes seen before, during and after this reaction were observed. Complete the sentences. Choose the answers from the box.

Sodium chloride (NaC l) is an ionic compound. Write the formulae of the ions in sodium chloride.

Complete the sentence. Choose the answer from the box.

Potassium is more reactive than sodium.

How does the size of a potassium atom compare with the size of a sodium atom? Give a reason for your answer.

This question is about the halogens.

Write the state symbol for chlorine at room temperature.

Figure 4 represents one molecule of fluorine. Complete the dot and cross diagram on Figure 4 You should show only the electrons in the outer shells.

19 A fluorine atom can be represented as 9 F What is the total number of electrons in a fluorine molecule (F₂)? Tick one box.

Aluminium reacts with bromine to produce aluminium bromide. Complete the balanced chemical equation for this reaction.

When chlorine reacts with potassium bromide, chlorine displaces bromine.

Explain why chlorine is more reactive than bromine.