Exothermic & endothermic reactions

This question is about temperature changes.

A student investigated the temperature changes as solids are dissolved in water.

This is the method used.

1. Measure 100 cm³ of water into a polystyrene cup.

2. Measure the temperature of the water.

3. Add 5.0 g of solid copper sulfate to the water.

4. Stir the mixture until all the copper sulfate has dissolved.

5. Measure the highest temperature reached by the mixture.

6. Repeat steps 1 to 5 with solid lithium chloride.

Draw one line from each measurement to the piece of equipment used to make the measurement.

Table 2 shows the highest temperature reached for each solid when dissolved in water.

Complete Figure 14.

You should:

use a suitable scale for the y-axis

plot the data for lithium chloride from Table 2 as a bar chart.

Before solid copper sulfate was added, the temperature of the water was 17 °C.

How do the results in Table 2 show that the process was exothermic?

The student used a different method to measure the temperature change when solid calcium chloride dissolved in water.

The student did four tests.

Table 3 shows the results.

Calculate mean value X in Table 3.

Figure 15 shows a reaction profile.

Which label on Figure 15 represents the products?

Tick () one box.

A B C D

Which label on Figure 15 represents the activation energy?

Tick () one box.

A B C D

Which label on Figure 15 represents the overall energy change?

Tick () one box.

A B C D

The elements in Group 1 of the periodic table are called the alkali metals.

Lithium reacts with chlorine to produce lithium chloride.

Figure 11 shows the reaction profile for the reaction between lithium and chlorine.

What do labels A, B and C on Figure 11 represent?

What type of reaction does the reaction profile in Figure 11 represent?

Describe what happens when a lithium atom reacts with a chlorine atom.

Answer in terms of electrons.

Explain the trend in the reactivity of the Group 1 metals.

A student investigated the reaction between citric acid powder and sodium hydrogen carbonate solution.

The temperature of the reaction mixture decreased.

Plan a method to investigate how changing the mass of citric acid affects the lowest temperature reached by the mixture.

The reaction between citric acid and sodium hydrogen carbonate is endothermic.

Which reaction profile represents an endothermic reaction?

Tick (✓) one box.

Explain why the rate of reaction is greater when powder is used instead of larger lumps.

Refer to surface area and collisions in your answer.

A student investigated the reaction between citric acid powder and sodium hydrogen carbonate solution.

The temperature of the reaction mixture decreased.

The reaction between citric acid and sodium hydrogen carbonate is endothermic.

Which reaction profile represents an endothermic reaction?

Tick (✓) one box.

Explain why the rate of reaction is greater when powder is used instead of larger lumps.

Refer to surface area and collisions in your answer.

This question is about metals reacting with oxygen.

Calcium (Ca) reacts with oxygen (O₂) to produce calcium oxide (CaO).

Balance the equation for the reaction.

______ Ca + O₂ → 2 CaO

40 g of calcium reacts completely with oxygen to produce 56 g of calcium oxide.

Calculate the maximum mass of calcium oxide that could be produced from 10 g of calcium.

A student reacted different masses of magnesium with oxygen and measured the mass of magnesium oxide produced.

Figure 3 shows the results.

Why did the student ignore one of the points when drawing the line of best fit on Figure 3 ?

Predict the mass of magnesium oxide produced from 0.5 g of magnesium.

You should extend the line of best fit on Figure 3.

A different student reacted copper with oxygen and measured the mass of copper oxide produced.

The student did repeat measurements for each mass of copper.

Table 1 shows the results when 0.42 g of copper was reacted.

Calculate mean value X in Table 1.

The reaction between copper and oxygen is exothermic.

Which reaction profile represents this reaction?

Tick (✓) one box.

This question is about the reaction between hydrochloric acid and sodium hydroxide solution.

A student investigated the effect of changing the volume of sodium hydroxide solution on the temperature change during the reaction.

This is the method used.

1. Measure 30 cm³ of hydrochloric acid into a polystyrene cup.

2. Measure the temperature of the hydrochloric acid.

3. Add 5 cm³ of sodium hydroxide solution.

4. Stir the mixture.

5. Measure the highest temperature the mixture reaches.

6. Repeat steps 1 to 5 three more times and calculate the mean temperature change.

7. Repeat steps 1 to 6 with different volumes of sodium hydroxide solution.

What two pieces of equipment should be used in this investigation?

Tick (✓) two boxes.

Balance

Measuring cylinder

Ruler

Stopclock

Thermometer

Table 1 shows the results for one volume of sodium hydroxide solution.

Calculate value X in Table 1.

Which type of error is reduced by repeating the tests and calculating the mean?

Tick (✓) one box.

Random

Systematic

Zero

A different student did the same investigation.

Figure 2 shows the results.

What was the mean temperature change when the volume of sodium hydroxide solution was 15 cm³?

Use Figure 2.

Give one conclusion from the results in Figure 2.

The reaction between hydrochloric acid and sodium hydroxide is exothermic.

Exothermic reactions give out energy.

Which reaction profile shows an exothermic reaction?

Tick (✓) one box.

Calculate the relative formula mass (M_r) of sodium hydroxide (NaOH).

Relative atomic masses (A_r): Na = 23 O = 16 H = 1

A student investigated the temperature increase when magnesium powder was added to copper sulfate solution.

Figure 17 shows the apparatus used.

This is the method used.

1. Add copper sulfate solution to a beaker.

2. Measure the initial temperature of the copper sulfate solution.

3. Add 0.1 g of magnesium powder.

4. Stir the mixture.

5. Measure the maximum temperature of the mixture.

6. Repeat steps 1 to 5 with different masses of magnesium powder.

Give two control variables the student should use.

Suggest one change to improve the accuracy of the investigation.

Table 4 shows the student’s results.

Explain the conclusions that can be made from the trends shown in the results.

Use data from Table 4 in your answer.

A student investigated the temperature increase when magnesium powder was added to copper sulfate solution.

Figure 3 shows the apparatus used.

This is the method used.

1. Add copper sulfate solution to a beaker.

2. Measure the initial temperature of the copper sulfate solution.

3. Add 0.1 g of magnesium powder.

4. Stir the mixture.

5. Measure the maximum temperature of the mixture.

6. Repeat steps 1 to 5 with different masses of magnesium powder.

Give two control variables the student should use.

Suggest one change to improve the accuracy of the investigation.

Table 1 shows the student’s results.

Explain the conclusions that can be made from the trends shown in the results.

Use data from Table 1 in your answer.

This question is about the reaction of metals with sulfuric acid.

The word equation for the reaction of zinc with sulfuric acid is:

zinc + sulfuric acid → zinc sulfate + hydrogen

What type of substance is zinc sulfate?

Tick (✓) one box.

Calculate the relative formula mass (M_r) of zinc sulfate (ZnSO₄).

Relative atomic masses (A_r): Zn = 65 S = 32 O = 16

A student investigated the temperature increase when the same mass of different metals were added to 0.1 M sulphuric acid.

The student used four different metals.

The student did the experiment three times for each metal and calculated the mean temperature increase for each metal.

Table 5 shows the results for nickel.

Calculate value X.

Table 6 shows the mean values for the four metals.

The student plotted the results on a bar chart.

Figure 9 shows the bar chart.

The student made some errors when plotting the bar chart.

Give three errors the student made.

Use Table 6 to place the metals in order of reactivity.

A teacher extracted copper from copper oxide.

This is the method used.

1. Mix 1.30 g of zinc and 1.59 g of copper oxide.

2. Heat the mixture strongly.

3. When the mixture starts to glow, stop heating.

4. Let the glow spread through the mixture.

5. Leave the mixture to cool.

This reaction is exothermic.

Which part of the method shows the reaction is exothermic?

Tick one box.

The equation for the reaction between zinc and copper oxide is:

1.30 g of zinc fully reacted with 1.59 g of copper oxide to produce 1.62 g of zinc oxide.

What mass of copper was produced?

What is the physical state of zinc oxide in the reaction?

Tick one box.

Which substance has been oxidised in the reaction?

Tick one box.

What type of reaction takes place when zinc reacts with copper oxide?

Tick one box.

Copper is a metal.

Which structure represents the arrangement of atoms in pure copper?

Tick one box.

Copper is used in electrical wiring.

Give one reason why.

In the UK, 40% of the copper we use is recycled copper.

The other 60% is copper obtained by mining.

What is the simplest ratio of recycled copper to copper obtained by mining?

Tick one box.

What are two advantages of recycling copper?

Tick two boxes.

A teacher demonstrated the temperature change when hydrochloric acid is added to sodium hydroxide.

This is the method used.

1. Add 25.0 cm³ of sodium hydroxide solution to a polystyrene cup.

2. Measure the temperature of the sodium hydroxide solution.

3. Add 25.0 cm³ of hydrochloric acid to the sodium hydroxide solution.

4. Stir the solution.

5. Measure the maximum temperature of the solution.

Draw one line from each measurement to the most suitable piece of equipment to use to make the measurement.

The teacher did the experiment four times.

Table 1 shows the teacher’s results.

Calculate the mean maximum temperature rise.

Do not use the anomalous result in your calculation.

How could the accuracy of the experiment be improved?

Tick one box.

The reaction between hydrochloric acid and sodium hydroxide is a neutralisation reaction.

The reaction produces a salt and one other product.

Complete the word equation for the reaction.

Universal indicator is used to measure the pH of solutions.

Hydrochloric acid is pH 1

Sodium hydroxide is pH 13

Draw one line from the pH to the colour of universal indicator in a solution with that pH.

This question is about hydrogen chloride.

A hydrogen atom contains 1 electron and a chlorine atom contains 17 electrons.

Complete Figure 7 to show a dot and cross diagram for a hydrogen chloride molecule.

Show the outer electrons only.

Hydrogen gas (H₂) reacts with chlorine gas to produce hydrogen chloride.

Complete the balanced chemical equation for the reaction between hydrogen and chlorine.

Figure 8 shows the reaction profile diagram for the reaction between hydrogen and chlorine.

What do A and B represent on Figure 8 ?

How does the reaction profile diagram show that the reaction is exothermic?

Hydrogen chloride gas dissolves in water to form hydrochloric acid.

Hydrochloric acid contains hydrogen ions and chloride ions.

Explain why hydrogen chloride gas does not conduct electricity but hydrochloric acid is able to conduct electricity.

A teacher demonstrated the extraction of copper from copper oxide.

This is the method used.

1. Mix 1.30 g of zinc and 1.59 g of copper oxide.

2. Heat the mixture strongly.

3. When the mixture starts to glow, stop heating.

4. Let the glow spread through the mixture.

5. Leave the mixture to cool.

6. Add hydrochloric acid to the cooled mixture.

7. Filter the mixture obtained in step 6.

A student concluded that an exothermic reaction had taken place.

Explain how an observation made during the demonstration shows this.

The equation for the reaction between zinc and copper oxide is:

1.59 g of copper oxide reacted.

Calculate the mass of copper produced.

Relative atomic masses (A_r): Cu = 63.5 O = 16 Zn = 65

Explain why steps 6 and 7 result in only copper being obtained as the residue.

The ionic equation for the reaction is:

Which statement about the reaction between zinc and copper ions is correct?

Tick one box.

A teacher demonstrated the temperature change when hydrochloric acid is added to sodium hydroxide solution.

This is the method used.

1. Measure 25 cm³ of sodium hydroxide solution using a measuring cylinder.

2. Add the sodium hydroxide solution to a polystyrene cup.

3. Record the temperature of the sodium hydroxide solution.

4. Add 5 cm³ of hydrochloric acid from a burette to the sodium hydroxide solution.

5. Stir the solution.

6. Record the temperature of the solution.

7. Repeat steps 4–6 until 50 cm³ of hydrochloric acid in total is added.

Table 1 shows some of the teacher’s results.

Figure 4 shows the results when 30 cm³ to 50 cm³ of hydrochloric acid was added to sodium hydroxide solution.

A line of best fit has been drawn through these results.

Complete Figure 4.

You should:

• plot the data from Table 1 on Figure 4

• draw a line of best fit through these results

• continue both lines of best fit until the lines meet.

Estimate the maximum temperature reached in the reaction.

Use Figure 4.

The teacher used a temperature sensor to measure the temperature of the reaction mixture.

What is the resolution of the temperature sensor?

Tick one box.

Suggest two ways of improving the accuracy of the results.

The pH of the solution changes as hydrochloric acid is gradually added to sodium hydroxide solution, until hydrochloric acid is in excess.

Describe how the pH of the solution changes.

Give reasons for these changes.

You should refer to the pH value of the solution at different stages in the procedure.

In a different demonstration the teacher used a 25 cm³ solution containing 1.4 g of sodium hydroxide.

Calculate the concentration of the sodium hydroxide solution in g/dm³