Tests for gases

Lithium reacts with chlorine to produce lithium chloride.

Figure 10 shows models of chlorine and of lithium chloride.

Draw one line from each substance to the type of bonding in the substance.

Lithium chloride can also be produced by reacting lithium carbonate with an acid.

Which acid reacts with lithium carbonate to produce lithium chloride?

Tick () one box.

Hydrochloric acid

Nitric acid

Sulfuric acid

What type of substance is lithium chloride?

Tick () one box.

Acid

Alkali

Salt

Figure 11 shows the electrolysis of lithium chloride solution.

Lithium chloride solution contains Li⁺ ions and Cl⁻ ions.

Chloride ions move to the positive electrode to produce chlorine.

Explain why chloride ions move to the positive electrode.

Hydrogen gas and chlorine gas are produced during the electrolysis of lithium chloride solution.

Draw one line from each gas to the result of the test for that gas.

Why is hydrogen gas produced at the negative electrode?

Tick () one box.

Hydrogen is less reactive than lithium.

Hydrogen has the same reactivity as lithium.

Hydrogen is more reactive than lithium.

Hydrogen reacts with chlorine to produce hydrogen chloride. A hydrogen atom has 1 electron in the outer shell.

A chlorine atom has 7 electrons in the outer shell.

Complete the dot and cross diagram for a hydrogen chloride molecule.

Use the symbols O and X to represent electrons.

A student investigated the reactivity of four metals with sulfuric acid.

Figure 13 shows the apparatus.

Give two variables the student should control.

Write the order of reactivity from least reactive to most reactive for the four metals.

Use Figure 13.

The gas produced in Figure 13 is hydrogen.

Describe the test for hydrogen gas.

Give the result if hydrogen is present.

The student repeated the investigation using different apparatus to determine the rate of reaction.

Figure 14 shows part of the apparatus.

Complete Figure 14 so that the apparatus can be used to determine the rate of reaction.

Give two measurements the student should make to determine the rate of reaction.

What is the unit for the rate of reaction determined using the apparatus in Figure 14

A student investigated the reactivity of four metals with sulfuric acid.

Figure 5 shows the apparatus.

Give two variables the student should control.

Write the order of reactivity from least reactive to most reactive for the four metals.

Use Figure 5.

The gas produced in Figure 5 is hydrogen.

Describe the test for hydrogen gas.

Give the result if hydrogen is present.

The student repeated the investigation using different apparatus to determine the rate of reaction.

Figure 6 shows part of the apparatus.

Complete Figure 6 so that the apparatus can be used to determine the rate of reaction.

Give two measurements the student should make to determine the rate of reaction.

What is the unit for the rate of reaction determined using the apparatus in Figure 6?

This question is about electrolysis.

Figure 9 shows the electrolysis of molten potassium chloride using inert electrodes.

Why must potassium chloride be molten during the electrolysis?

Why are inert electrodes used in electrolysis?

A gas is released during the electrolysis of molten potassium chloride.

Describe the test to identify the gas released.

Give the result if the gas is present.

Potassium is produced at the negative electrode.

Write the half equation for the reaction at the negative electrode during the electrolysis of molten potassium chloride.

What type of reaction occurs at the negative electrode?

An aqueous solution of potassium chloride was electrolysed.

Hydrogen gas was produced at the negative electrode.

Explain why hydrogen gas is produced during the electrolysis of an aqueous solution of potassium chloride.

50 cm³ of potassium chloride solution contains 0.030 moles of potassium chloride.

Calculate the concentration of the potassium chloride solution in g/dm³.

Relative formula mass (M_r) of potassium chloride = 74.5

Concentration = g/dm³ _________________

Magnesium reacts with hydrochloric acid.

A student investigated the effect of changing the hydrochloric acid concentration on the rate of this reaction.

Figure 22 shows the apparatus.

This is the method used.

1. Add 50 cm³ of hydrochloric acid to the conical flask.

2. Add a 3 cm strip of magnesium to the hydrochloric acid in the conical flask.

3. Fit the stopper and delivery tube to the top of the conical flask and start timing.

4. Record the volume of hydrogen gas collected in the measuring cylinder every 20 seconds for a total of 100 seconds.

5. Repeat steps 1 to 4 with a different concentration of hydrochloric acid.

The stopper and delivery tube were fitted to the conical flask in step 3.

Explain why the time taken to fit the stopper and delivery tube may cause an error in this investigation.

Figure 23 shows the results for one concentration of hydrochloric acid.

Determine the time taken for the reaction to be complete.

Use Figure 23.

The student repeated the method using a higher concentration of hydrochloric acid.

How would the line of best fit for a higher concentration of hydrochloric acid compare with the line of best fit on Figure 23 ?

Tick (✓) one box.

Initially the line of best fit would have a lower gradient.

Initially the line of best fit would have the same gradient.

Initially the line of best fit would have a higher gradient.

Describe the test for hydrogen gas.

Give the result of the test.

Magnesium reacts with hydrochloric acid.

A student investigated the effect of changing the hydrochloric acid concentration on the rate of this reaction.

Figure 2 shows the apparatus.

This is the method used.

1. Add 50 cm³ of hydrochloric acid to the conical flask.

2. Add a 3 cm strip of magnesium to the hydrochloric acid in the conical flask.

3. Fit the stopper and delivery tube to the top of the conical flask and start timing.

4. Record the volume of hydrogen gas collected in the measuring cylinder every 20 seconds for a total of 100 seconds.

5. Repeat steps 1 to 4 with a different concentration of hydrochloric acid.

The stopper and delivery tube were fitted to the conical flask in step 3.

Explain why the time taken to fit the stopper and delivery tube may cause an error in this investigation.

Figure 3 shows the results for one concentration of hydrochloric acid.

Determine the time taken for the reaction to be complete.

Use Figure 3.

The student repeated the method using a higher concentration of hydrochloric acid.

How would the line of best fit for a higher concentration of hydrochloric acid compare with the line of best fit on Figure 3 ?

Tick (✓) one box.

Initially the line of best fit would have a lower gradient.

Initially the line of best fit would have the same gradient.

Initially the line of best fit would have a higher gradient.

Describe the test for hydrogen gas.

Give the result of the test.

Magnesium and hydrochloric acid react to produce magnesium chloride and hydrogen.

Give the test for hydrogen gas.

Give the result of the test if hydrogen gas is present.

During the reaction between magnesium and hydrochloric acid, hydrogen ions form hydrogen molecules.

The half equation for this process is:

What type of reaction does this half equation show?

Give the reason for your answer.

0.72 g of magnesium reacted completely with dilute hydrochloric acid.

The equation for the reaction is:

Calculate the mass of magnesium chloride produced.

Relative atomic masses (A_r): Mg = 24 Cl = 35.5

This question is about the extraction of metals.

Traditional mining methods extract copper from high-grade copper ores.

Phytomining is a method used to extract copper from low-grade copper ores.

Explain one advantage of using phytomining compared with using traditional mining methods to extract copper.

Do not refer to cost in your answer.

Describe how copper compounds are obtained by phytomining.

Electrolysis is one method of obtaining copper from solutions of copper compounds.

Figure 6 shows the apparatus used.

Graphite is a good conductor of electricity.

Give one other reason why graphite is used for the electrodes.

A gas is produced at the positive electrode. The gas is tested with damp litmus paper. The gas bleaches the damp litmus paper.

Identify the copper compound in solution.

Give one reason for your answer.

Scrap iron is used in a reaction to obtain copper from solutions of copper compounds.

Name this type of reaction.

Aluminium is extracted by the electrolysis of a molten mixture of aluminium oxide and cryolite.

Explain why a mixture rather than pure aluminium oxide is electrolysed.

The positive electrodes are made of carbon.

Explain why the positive electrodes wear away during the process.

This question is about electrolysis.

A student investigated the electrolysis of aqueous solutions using inert electrodes.

Figure 3 shows the apparatus used.

The electrodes are made of graphite.

Which element is graphite a form of?

Tick (✓) one box.

Aluminium

Carbon

Copper

Silicon

The electrodes are inert.

What does ‘inert’ mean?

What is meant by an ‘aqueous solution’?

The student electrolysed four aqueous solutions.

Table 2 shows some of the results.

Complete Table 2.

Choose answers from the box.

What would you use to test for chlorine gas?

Tick (✓) one box.

A burning splint

A glowing splint

Damp litmus paper

A student investigated the electrolysis of potassium chloride solution.

Figure 1 shows the apparatus used.

The student used the piece of equipment labelled A to measure the volume of gas collected.

What is the piece of equipment labelled A ?

Tick (✓) one box.

What does the circuit symbol B represent?

Complete the sentence.

Choose the answer from the box.

Direct current (dc) is supplied to the circuit.

What is direct current?

Tick (✓) one box.

Potassium chloride solution contains potassium (K⁺) ions and chloride (Cl^–) ions.

Why are chloride ions attracted to the positive electrode?

Hydrogen gas is produced at the negative electrode.

Which test should the student use to identify hydrogen gas?

Tick (✓) one box.

Hydrogen ions and potassium ions move to the negative electrode.

Hydrogen gas is produced at the negative electrode.

Why is hydrogen gas produced at the negative electrode?

Tick (✓) one box.

The student measured the volume of gas collected at each electrode every minute for 25 minutes.

Figure 2 shows the results.

Describe one similarity and one difference in the volume of hydrogen and the volume of chlorine collected during the 25 minutes.

Use Figure 2.

Catalase is an enzyme.

What type of molecule is an enzyme?

Hydrogen peroxide decomposes in the presence of catalase.

This is the equation for the reaction:

Describe how the student could test for the gas produced.

A student investigated the effect of pH on the activity of catalase.

Describe how the student could use an indicator to measure the pH of a solution.

Table 6 shows the results.

What is the optimum pH for catalase in this reaction?

Use Table 6.

How could the student find a more accurate value for the optimum pH?

Tick (✓) one box.

Explain the result for catalase at pH 3.0

Catalase is an enzyme.

What type of molecule is an enzyme?

Hydrogen peroxide decomposes in the presence of catalase.

This is the equation for the reaction:

Describe how the student could test for the gas produced.

A student investigated the effect of pH on the activity of catalase.

Describe how the student could use an indicator to measure the pH of a solution.

Table 1 shows the results.

What is the optimum pH for catalase in this reaction?

Use Table 1.

How could the student find a more accurate value for the optimum pH?

Tick (✓) one box.

Explain the result for catalase at pH 3.0