Rate of reaction

When marble chips react with an acid, they produce a colourless solution and a gas.

Which method is used to determine the rate of reaction?

A A disappearing cross experiment

B Gas chromatography

C Measuring the mass loss using a balance

D Measuring the volume of solution produced

The graph shows the volume of gas produced during a reaction.

A tangent has been drawn at 50 seconds. The gradient of the tangent gives the rate of reaction.

What is the rate of reaction, in cm³ / s, at 50 seconds?

A 0.56

B 0.70

C 1.1

D 1.4

The graph shows the volume of gas produced during a reaction.

A tangent has been drawn at 50 seconds. The gradient of the tangent gives the rate of reaction.

What is the rate of reaction, in cm³ / s, at 50 seconds?

A 0.56

B 0.70

C 1.1

D 1.4

15* A student investigates the rate of reaction between pieces of marble chips and an excess of dilute hydrochloric acid.

The diagram shows the equipment they use.

The student measures the total volume of carbon dioxide gas produced every minute until the reaction finishes.

They do two different experiments and plot a graph of the results.

Which experiment has the greater rate of reaction?

Explain your answer by including:

• information from the graph

• a description of how the experiments might be different

• ideas about the reacting particle model including particles and their collisions.

A student investigates the rate of reaction between marble chips and dilute hydrochloric acid.

The graph shows how the mass of the reactants changes during the reaction.

What are the units for the rate of reaction?

A g

B g/s

C s

D s/g

16* A student investigates the rate of reaction between magnesium and an excess of dilute hydrochloric acid.

Strip of magnesium
Dilute hydrochloric acid

The student does three experiments. In the experiments they use the same length of magnesium but change one other variable.

The table shows the results of the three experiments.

Describe the method the student used to get these results, including the variable they may have changed and the variables they controlled.

The student has difficulty filling the measuring cylinder with water.

They change the measuring cylinder for a different piece of apparatus which allows them to measure the volume of hydrogen more accurately.

Name the piece of apparatus they use and complete the diagram below to show this apparatus.

Name of piece of apparatus........

Complete the balanced symbol equation for the reaction.

The student repeats the experiment. The only difference is they use a higher concentration of acid.

Draw a line on the graph to show the results of this experiment.

If the experiment is repeated at a higher temperature, the rate of reaction increases.

Explain why. Use ideas about particles and collisions.

When marble chips react with dilute hydrochloric acid, the mass of the reactants decreases.

The graph shows the loss in mass of the reactants with time.

What is the correct formula used to calculate the mean rate of reaction between 2 and 4 minutes?

The student has difficulty filling the measuring cylinder with water.

They change the measuring cylinder for a different piece of apparatus which allows them to measure the volume of hydrogen more accurately.

Name the piece of apparatus they use and complete the diagram below to show this apparatus.

Name of piece of apparatus........

Complete the balanced symbol equation for the reaction.

The student repeats the experiment. The only difference is they use a higher concentration of acid.

Draw a line on the graph to show the results of this experiment.

If the experiment is repeated at a higher temperature, the rate of reaction increases.

Explain why. Use ideas about particles and collisions.

A student investigates the rate of reaction between large pieces of calcium carbonate and dilute hydrochloric acid.

Fig. 13.1 shows two different experiments the student could use. In both experiments the mass decreases as the reaction progresses.

Fig. 13.1

The equation shows the reaction between calcium carbonate and hydrochloric acid.

Use this equation to explain why the mass decreases as the reaction progresses.

The student decides to use Experiment 2 because they think it will produce more accurate results than Experiment 1.

Explain why the student is correct.

The student repeats Experiment 2 with smaller pieces of calcium carbonate to see how this changes the rate of the reaction.

Describe two variables the student must keep the same in this experiment.

Describe and explain the effect of using smaller pieces of calcium carbonate on the rate of the reaction.

The gradient of the tangent gives the rate of reaction. Use the tangent to calculate the rate of reaction at the start of the reaction.

Give your answer to 1 decimal place.

Rate of reaction =........ cm³ / minute

What happens to the rate of reaction as the reaction progresses?

Explain your answer using ideas about particles and collisions.

Another student repeats the experiment.

They increase the concentration of the dilute hydrochloric acid. They keep everything else in the experiment the same.

Does the gradient of the graph at the start of this student’s reaction decrease, increase or stay the same compared to the first student’s experiment?

Tick (✓) one box.

Give a reason for your answer.

Write down the volume of hydrogen gas that is produced at the end of this reaction.

The gradient of the tangent gives the rate of reaction. Use the tangent to calculate the rate of reaction at the start of the reaction.

Give your answer to 1 decimal place.

Rate of reaction =........ cm³ / minute

What happens to the rate of reaction as the reaction progresses?

Explain your answer using ideas about particles and collisions.

Another student repeats the experiment.

They increase the concentration of the dilute hydrochloric acid. They keep everything else in the experiment the same.

Does the gradient of the graph at the start of this student’s reaction decrease, increase or stay the same compared to the first student’s experiment?

Tick (✓) one box.

Give a reason for your answer.

Write down the volume of hydrogen gas that is produced at the end of this reaction.

A student investigates the rate of a reaction at different concentrations.

Fig. 12.1 shows the apparatus he uses.

The student adds dilute hydrochloric acid to the sodium thiosulfate solution. He times how long it takes for the cross to disappear. This is the reaction time.

The student repeats the experiment at different concentrations of sodium thiosulfate solution.

The concentration of hydrochloric acid is the same in each experiment.

He plots the results of the experiment on a graph, as shown in Fig. 12.2.

Look at the equation for the reaction.

Na₂S₂O₃(aq) + 2HCl (aq) → 2NaCl (aq) + H₂O(l) + S(s) + SO₂(g)

Which product in the reaction makes the cross disappear?

Tick (✓) one box.

The rate of reaction can be calculated using the equation:

Use the graph in Fig. 12.2 to calculate the rate of reaction when the concentration of sodium thiosulfate solution is 0.25 mol / dm³.

Give your answer to 2 decimal places.

Rate of reaction =........ / s

Describe the trend shown by the graph in Fig. 12.2.

State how the rate of reaction changes as the sodium thiosulfate concentration changes.

Another student investigates the effect of temperature on the rate of reaction.

She calculates the rate of reaction at different temperatures, as shown in the table.

Predict the rate of reaction at 70 °C.

Predicted rate of reaction =........ / s

A teacher adds calcium carbonate to an acid in four separate flasks, A, B, C and D.

He measures the time it takes for the same volume of carbon dioxide to be produced in each flask.

This is a graph of his results.

Which flask has the fastest rate of reaction?

A student investigates the rate of reaction between marble chips and hydrochloric acid.

Both experiments use 50 cm³ of hydrochloric acid and an excess of marble chips.

He measures the total mass of carbon dioxide given off for different sizes of marble chips.

Look at his results.

The student has plotted his results for the large marble chips on the graph.

Plot the results for the small marble chips.

Draw a line of best fit.

Look at the line for the large marble chips.

How long does it take for the reaction to finish?

Answer =........ minutes

What mass of carbon dioxide is given off after 15 minutes?

The reaction is faster with small marble chips.

Write down two ways that the graph shows this is correct.

Both small and large marble chips give off the same mass of carbon dioxide at the end of the experiments.

Suggest why.

A balance was used to measure the amount of carbon dioxide given off.

Write down the name of a different piece of equipment that could be used to measure the amount of carbon dioxide produced.

A student investigates the rate of reaction between magnesium and hydrochloric acid. The reaction gives off hydrogen gas.

The student wants to investigate how changing the concentration of the hydrochloric acid affects the rate of reaction.

Look at her plan.

I will put 0.5 g of magnesium ribbon into the flask.

I will add 50 cm³ of hydrochloric acid.

I will measure how fast the gas is given off.

I will put another 0.5 g of magnesium ribbon into the flask.

I will add 100 cm³ of the same hydrochloric acid.

I will measure how fast the gas is given off.

Another student thinks that the plan will not work and he does not understand exactly what he has to do.

Suggest how the plan for this investigation can be improved.

A student investigates the rate of reaction between magnesium and hydrochloric acid. The reaction gives off hydrogen gas.

The student wants to investigate how changing the concentration of the hydrochloric acid affects the rate of reaction.

Look at her plan.

I will put 0.5 g of magnesium ribbon into the flask.

I will add 50 cm³ of hydrochloric acid.

I will measure how fast the gas is given off.

I will put another 0.5 g of magnesium ribbon into the flask.

I will add 100 cm³ of the same hydrochloric acid.

I will measure how fast the gas is given off.

Another student thinks that the plan will not work and he does not understand exactly what he has to do.

Suggest how the plan for this investigation can be improved.

A student investigates the rate of reaction between marble chips and hydrochloric acid.

He measures the total mass of carbon dioxide given off for different sizes of marble chips.

Look at a graph of his results.

Which reaction is faster?

Explain how you can tell using data from the graph.

Explain why changing the size of the marble chips changes the rate of the reaction.