Identification of ions

This question is about chemical analysis.

Some metal ions can be identified using a flame test.

Describe how to do a flame test using a metal wire and a Bunsen burner.

Draw one line from each metal ion to the flame colour produced by the metal ion.

Which gas is produced when carbonates are reacted with dilute acids?

Tick () one box.

Which solution is used to test for sulfate ions?

Tick () one box.

Precipitates are used to identify some ions.

Complete the sentence.

Choose the answer from the box.

gas liquid solid

Some metal ions in solution can be identified by adding sodium hydroxide solution.

Draw one line from each metal ion to the colour of the precipitate produced by the metal ion.

Dilute nitric acid and silver nitrate solution were added to a solution containing iodide ions.

Complete the sentence.

Choose the answer from the box.

A student analysed three solutions, A, B and C.

Each solution contained one ionic compound.

The student added a few drops of sodium hydroxide solution to solution A.

Solution A produced a white precipitate.

Aluminium ions produce a white precipitate with a few drops of sodium hydroxide solution.

Name one other metal ion which produces a white precipitate with a few drops of sodium hydroxide solution.

Describe how the student could confirm the presence of aluminium ions in solution A

Give the result of the test.

The student tested solution B to identify the ions present.

The student did a flame test on solution B.

An orange-red flame was produced.

Write the symbol for the metal ion in solution B.

The student added dilute nitric acid followed by silver nitrate solution to solution B.

A white precipitate was produced.

Write the symbol for the non-metal ion in solution B.

The student added 1.0 mol/dm³ nitric acid to solution C.

Bubbles of gas were produced.

Describe a test on the bubbles of gas that confirms that solution C contained carbonate ions.

Give the result of the test.

The student repeated the test on solution C using 1.0 mol/dm³ ethanoic acid instead of 1.0 mol/dm³ nitric acid.

Bubbles of gas were produced more slowly using ethanoic acid.

Explain why.

This question is about materials.

Pre-stressed concrete is a composite material.

The concrete is strengthened using high carbon steel bars.

Figure 8 shows the structure of a piece of pre-stressed concrete.

Which two words describe the high carbon steel bars?

Tick (✓) two boxes.

Limestone is mainly calcium carbonate.

Limestone is a raw material used in the production of concrete.

In the first part of the production of concrete:

• air is heated by burning methane

• the hot air is used to heat limestone

• the limestone decomposes.

The equation for the decomposition of limestone is:

calcium carbonate → calcium oxide + carbon dioxide

Give two ways in which a greenhouse gas is released in this process.

How could a sample of limestone be tested to show the presence of carbonate ions?

Complete the sentences.

Choose answers from the box.

The substance added to the limestone is

The gas produced is identified using

Table 4 gives some information about plain concrete and pre-stressed concrete.

Explain why pre-stressed concrete rather than plain concrete is used to make bridges that carry heavy lorries.

Use Table 4.

Figure 9 shows a garden path made of plain concrete slabs.

Suggest two reasons why plain concrete rather than pre-stressed concrete is used to make slabs for garden paths.

Use Table 4.

A student investigated an aqueous solution of a salt.

The student identified that the salt solution contained only sodium ions and chloride ions.

Describe a test to identify sodium ions.

Give the result of the test.

Test for sodium ions

Describe a test to identify chloride ions.

Give the result of the test.

Test for chloride ions

The student determined the concentration of sodium chloride in the salt solution.

This is the method used.

1. Weigh an empty evaporating dish.

2. Add 25.0 cm³ of the salt solution into the evaporating dish.

3. Heat the evaporating dish and contents.

4. Weigh the evaporating dish and contents.

5. Repeat steps 3 to 4 until there is no further change in mass.

6. Repeat steps 1 to 5 three more times.

Why did the student heat the evaporating dish and contents until the mass did not change?

How did the student calculate the mass of solid sodium chloride remaining after steps 1 to 5?

Tick (✓) one box.

The student calculated the concentration of sodium chloride in the salt solution.

Table 5 shows the results.

The percentage by mass of sodium ions in sodium chloride is 39.3%.

Calculate the mean concentration of sodium ions in the salt solution.

A student investigated an aqueous solution of a salt.

The student identified that the salt solution contained only sodium ions and chloride ions.

Describe a test to identify sodium ions.

Give the result of the test.

Test for sodium ions

Describe a test to identify chloride ions.

Give the result of the test.

Test for chloride ions

The student determined the concentration of sodium chloride in the salt solution.

This is the method used.

1. Weigh an empty evaporating dish.

2. Add 25.0 cm³ of the salt solution into the evaporating dish.

3. Heat the evaporating dish and contents.

4. Weigh the evaporating dish and contents.

5. Repeat steps 3 to 4 until there is no further change in mass.

6. Repeat steps 1 to 5 three more times.

Why did the student heat the evaporating dish and contents until the mass did not change?

How did the student calculate the mass of solid sodium chloride remaining after steps 1 to 5?

Tick (✓) one box.

The student calculated the concentration of sodium chloride in the salt solution.

Table 1 shows the results.

The percentage by mass of sodium ions in sodium chloride is 39.3%.

Calculate the mean concentration of sodium ions in the salt solution.

This question is about sulfuric acid.

Sulfuric acid contains sulfate ions.

Describe the test for the presence of sulfate ions in sulfuric acid.

Give the result of the test.

One stage in the industrial production of sulfuric acid is the reaction of sulfur dioxide with oxygen to produce sulfur trioxide.

This reversible reaction reaches dynamic equilibrium.

Figure 7 shows the percentage yield of sulfur trioxide in this reaction at different temperatures.

Which statement about the forward reaction is correct?

Use Figure 7.

Tick (✓) one box.

The equation for the reaction is:

Explain why the percentage yield of sulfur trioxide in this reaction is greater if the pressure is higher.

In industry, the reaction is done at 450 °C and atmospheric pressure.

Under these conditions the yield of sulfur trioxide is 86%.

Suggest two reasons why a higher pressure is not used.

This reaction uses a catalyst to increase the rate of the reaction.

The catalyst is a metal oxide.

Which is the most likely metal in the metal oxide catalyst?

Use the periodic table.

Tick (✓) one box.

This question is about chemical analysis.

Potassium bromide is used in medicine.

A scientist tested a sample of medicine to show the presence of potassium ions and of bromide ions.

The sample is soluble in water.

Plan a method the scientist could use to show that the sample of medicine contains potassium ions and bromide ions.

The scientist has:

• a Bunsen burner

• a metal wire

• test tubes

• a dropping pipette

• distilled water

• dilute nitric acid

• silver nitrate solution.

You should give the results of the tests.

The scientist could also use an instrumental method to show the presence of potassium ions in the medicine.

Which instrumental method could be used to show the presence of potassium ions in the medicine?

Give one advantage of using this instrumental method instead of a chemical test.

This question is about chemical analysis. Potassium bromide is used in medicine. A scientist tested a sample of medicine to show the presence of potassium ions and of bromide ions. The sample is soluble in water.

Plan a method the scientist could use to show that the sample of medicine contains potassium ions and bromide ions. The scientist has:

• a Bunsen burner

• a metal wire

• test tubes

• a dropping pipette

• distilled water

• dilute nitric acid

• silver nitrate solution.

You should give the results of the tests.

The scientist could also use an instrumental method to show the presence of potassium ions in the medicine.

Which instrumental method could be used to show the presence of potassium ions in the medicine?

Give one advantage of using this instrumental method instead of a chemical test.

Copper is extracted from metal ores. Chalcopyrite is a metal ore containing a compound with the formula CuFeS₂

CuFeS₂ reacts with oxygen to produce copper(II) sulfate and iron(II) sulfate. Complete the equation for this reaction. You should balance the equation.

Calculate the percentage by mass of copper in CuFeS₂ Relative atomic masses (A_r): S = 32 Fe = 56 Cu = 63.5

Describe a test to show the presence of copper(II) ions in a solution of copper(II) sulfate. Give the result of the test.

Copper can be extracted from low-grade ores by bioleaching. Describe what is meant by bioleaching.

This question is about water.

A student investigated pure water. The student measured:

• the boiling point of pure water

• the pH of pure water.

Complete the sentences. Choose answers from the box.

What could the student use to measure the pH of pure water?

A different student investigated sea water. Sea water contains dissolved solids.

This is the method used.

1. Measure a 50 cm³ sample of the sea water.

2. Heat the sample until all the water has evaporated.

3. Measure the mass of solid that remains.

4. Repeat steps 1 to 3 three more times.

Which two pieces of equipment were needed in this investigation? Tick (✓) two boxes.

Table 1 shows the results.

Calculate the mean mass of solid that remained.

A 50 cm³ sample of sea water from a different source contained 1.50 g of dissolved solids. Calculate the mass of dissolved solids in 1000 cm³ of this sea water.

Sodium chloride is a dissolved solid in sea water. Sodium chloride contains sodium ions and chloride ions.

Complete the sentence. Choose the answer from the box.

The student tested sea water for sodium ions using a flame test.

Complete the sentence. Choose the answer from the box.

The student tested sea water for chloride ions by adding nitric acid and silver nitrate solution.

This question is about copper wire and copper compounds.

Copper is used to make electrical wires. Figure 9 shows how copper electrical wire is insulated using an addition polymer called poly(butene).

The addition polymer poly(butene) has the displayed structural formula:

Poly(butene) is produced from the monomer butene. Complete Figure 10 to show the displayed structural formula of butene.

Copper can be obtained by recycling scrap copper wire.

Suggest why poly(butene) insulation must be removed from scrap copper wire before the copper is recycled.

Describe how scrap copper wire can be recycled to make new copper water pipes.

Suggest two reasons why recycling scrap copper is more sustainable than extracting copper from copper ores.

Copper sulfate is a compound of copper. Copper sulfate solution contains copper(II) ions and sulfate ions.

A solution can be added to copper sulfate solution to show the presence of copper(II) ions. Name the solution added. Give the result of the test. Name of solution added

Describe one test to show the presence of sulfate ions in copper sulfate solution. Give the result of the test.

This question is about copper wire and copper compounds.

Copper is used to make electrical wires. Figure 1 shows how copper electrical wire is insulated using an addition polymer called poly(butene).

The addition polymer poly(butene) has the displayed structural formula:

Poly(butene) is produced from the monomer butene. Complete Figure 2 to show the displayed structural formula of butene.

Copper can be obtained by recycling scrap copper wire.

Suggest why poly(butene) insulation must be removed from scrap copper wire before the copper is recycled.

Describe how scrap copper wire can be recycled to make new copper water pipes.

Suggest two reasons why recycling scrap copper is more sustainable than extracting copper from copper ores.

Copper sulfate is a compound of copper. Copper sulfate solution contains copper(II) ions and sulfate ions.

A solution can be added to copper sulfate solution to show the presence of copper(II) ions. Name the solution added. Give the result of the test. Name of solution added

Describe one test to show the presence of sulfate ions in copper sulfate solution. Give the result of the test.

Potash alum is a chemical compound.

Potash alum contains potassium ions, aluminium ions and sulfate ions.

Which two methods can be used to identify the presence of potassium ions in potash alum solution?

Tick (✓) two boxes.

Sodium hydroxide solution is used to test for some metal ions.

Sodium hydroxide solution is added to a solution of potash alum until a precipitate forms.

Complete the sentence.

Choose the answer from the box.

Complete the sentence.

Choose the answer from the box.

Sulfate ions can be identified using dilute hydrochloric acid

and.

A solution of potash alum has a concentration of 258 g/dm³

Calculate the mass of potash alum needed to make 800 cm³ of a solution of potash alum with a concentration of 258 g/dm³

Give your answer to 3 significant figures.

Potash alum is a chemical compound. The formula of potash alum is KAl(SO₄)₂

Give a test to identify the Group 1 metal ion in potash alum. You should include the result of the test.

Name one instrumental method that could identify the Group 1 metal ion and show the concentration of the ion in a solution of potash alum.

A student identifies the other metal ion in potash alum. The student tests a solution of potash alum by adding sodium hydroxide solution until a change is seen.

Give the result of this test.

This test gives the same result for several metal ions. What additional step is needed so that the other metal ion in potash alum can be identified? Give the result of this additional step.

Describe a test to identify the presence of sulfate ions in a solution of potash alum. Give the result of the test.

This question is about chemical analysis.

A student tested copper sulfate solution and calcium iodide solution using flame tests.

This is the method used.

1. Dip a metal wire in copper sulfate solution.

2. Put the metal wire in a blue Bunsen burner flame.

3. Record the flame colour produced.

4. Repeat steps 1 to 3 using the same metal wire but using calcium iodide solution.

What flame colour is produced by copper sulfate solution?

Calcium compounds produce an orange-red flame colour.

The student left out an important step before reusing the metal wire.

The student’s method did not produce a distinct orange-red flame colour using calcium iodide solution.

Explain why.

The student added sodium hydroxide solution to:

• copper sulfate solution

• calcium iodide solution.

Give the results of the tests.

Copper sulfate solution

Calcium iodide solution

To test for sulfate ions the student added dilute hydrochloric acid to copper sulfate solution.

Name the solution that would show the presence of sulfate ions when added to this mixture.

To test for iodide ions the student added dilute nitric acid to calcium iodide solution.

Name the solution that would show the presence of iodide ions when added to this mixture.

Give the result of the test.

This question is about chemical analysis.

A student tested copper sulfate solution and calcium iodide solution using flame tests. This is the method used.

1. Dip a metal wire in copper sulfate solution.

2. Put the metal wire in a blue Bunsen burner flame.

3. Record the flame colour produced.

4. Repeat steps 1 to 3 using the same metal wire but using calcium iodide solution.

What flame colour is produced by copper sulfate solution?

Calcium compounds produce an orange-red flame colour. The student left out an important step before reusing the metal wire. The student’s method did not produce a distinct orange-red flame colour using calcium iodide solution. Explain why.

The student added sodium hydroxide solution to:

• copper sulfate solution

• calcium iodide solution.

Give the results of the tests. Copper sulfate solution

Calcium iodide solution

To test for sulfate ions the student added dilute hydrochloric acid to copper sulfate solution. Name the solution that would show the presence of sulfate ions when added to this mixture.

To test for iodide ions the student added dilute nitric acid to calcium iodide solution. Name the solution that would show the presence of iodide ions when added to this mixture. Give the result of the test.

This question is about drinking water.

There are two main steps in producing drinking water from fresh water.

Draw one line from each step to the reason for the step.

Which two substances are used to sterilise fresh water?

Tick (✓) two boxes.

A large amount of aluminium sulfate was accidentally added to the drinking water supply at a water treatment works.

Scientists tested a sample of the drinking water to show that it contained dissolved solids.

Which two methods show the presence of dissolved solids in the sample of drinking water?

Tick (✓) two boxes.

Scientists tested two water samples from the drinking water supply.

The scientists tested one sample for aluminium ions and the other sample for sulfate ions.

Draw one line from each ion to the compound needed to identify the ion.

How could pure water be produced from drinking water that contained dissolved solids?

Tick (✓) one box.

This question is about lithium carbonate.

Lithium carbonate is used in medicines.

Figure 7 shows a tablet containing lithium carbonate.

Lithium carbonate contains lithium ions and carbonate ions.

A student tested the tablet for lithium ions and for carbonate ions.

The student used:

• a metal wire

• dilute hydrochloric acid

• limewater.

Plan an investigation to show the presence of lithium ions and of carbonate ions in the tablet.

You should include the results of the tests for the ions.

The tablet also contains other substances.

The substances in tablets are present in fixed amounts.

What name is given to mixtures like tablets?

The tablet has a mass of 1.20 g and contains 700 mg of lithium carbonate.

Calculate the percentage by mass of lithium carbonate in this tablet.

This question is about lithium carbonate.

Lithium carbonate is used in medicines.

Figure 2 shows a tablet containing lithium carbonate.

Lithium carbonate contains lithium ions and carbonate ions.

A student tested the tablet for lithium ions and for carbonate ions.

The student used:

• a metal wire

• dilute hydrochloric acid

• limewater.

Plan an investigation to show the presence of lithium ions and of carbonate ions in the tablet.

You should include the results of the tests for the ions.

The tablet also contains other substances.

The substances in tablets are present in fixed amounts.

What name is given to mixtures like tablets?

The tablet has a mass of 1.20 g and contains 700 mg of lithium carbonate.

Calculate the percentage by mass of lithium carbonate in this tablet.

A large amount of aluminium sulfate was accidentally added to the drinking water supply at a water treatment works.

Describe a test to show that the drinking water contained aluminium ions.

Give the result of the test.

Describe a test to show that the drinking water contained sulfate ions.

Give the result of the test.

Plan an investigation to find the total mass of dissolved solids in a 100 cm³ sample of the drinking water.

Your investigation should produce valid results.

This question is about chemicals in fireworks. Coloured flames are produced because of the metal ions present in fireworks.

What colour flame would sodium ions produce?

Name a metal ion that would produce a green flame.

Some fireworks contain a mixture of metal ions. Why is it difficult to identify the metal ions from the colour of the flame?

Flame emission spectroscopy is used to identify metal ions in a firework. Figure 1 shows:

• the flame emission spectra of five individual metal ions

• a flame emission spectrum for a mixture of two metal ions.

Which two metal ions are in the mixture? Tick two boxes.

The compounds in fireworks also contain non-metal ions. A scientist tests a solution of the chemicals used in a firework.

Silver nitrate solution and dilute nitric acid are added to the solution. A cream precipitate forms. Which ion is shown to be present by the cream precipitate?

Describe a test to show the presence of sulfate ions in the solution. Give the result of the test if there are sulfate ions in the solution.