Collision theory & activation energy

A student uses this apparatus to investigate the rate of reaction between marble chips and dilute hydrochloric acid.

This is the equation for the reaction.

Give a reason why the reading on the balance decreases during the reaction.

Explain why the rate of reaction is greatest at the start.

After 10 minutes, the reaction stops even though there are marble chips remaining.

Give a reason why the reaction stops.

The student repeats the experiment with hydrochloric acid at a higher temperature to investigate the effect on the rate of reaction.

Give two variables that should be controlled to make sure the results are valid.

Explain the effect of increasing the temperature of hydrochloric acid on the rate of reaction.

A student uses this apparatus to investigate the rate of reaction between dilute sulfuric acid and an excess of small pieces of zinc.

This is the student’s method.

Step 1 use 50 cm³ of dilute sulfuric acid

Step 2 add approximately 5 g of small zinc pieces to the sulfuric acid

Step 3 quickly connect the gas syringe

Step 4 record the reading on the gas syringe every 30 seconds until the reaction stops

Name a suitable piece of apparatus to measure the volume of sulfuric acid.

Give a reason why the mass of zinc pieces does not need to be measured accurately.

Give a reason why the student quickly connects the gas syringe in step 3.

State how the student would know when the reaction stops.

The graph shows the volume of gas collected in the syringe during the experiment.

A tangent to the curve has been drawn at a time of 80 s.

Use the tangent to calculate the rate of reaction at 80 s.

Show your working on the graph.

Give the unit.

Explain the shape of the graph in these regions.

from 0 s to 60 s

from 60 s to 150 s

from 150 s to 240 s

This question is about sulfur.

The diagram represents the electronic configuration of an atom of sulfur.

Which period of the Periodic Table contains sulfur?

What is the charge on a sulfide ion?

When a mixture of sulfur and zinc is heated to a high temperature a reaction occurs, forming the compound zinc sulfide, ZnS

Give a reason why the mixture of sulfur and zinc needs heating before a reaction occurs.

Calculate the relative formula mass (M_r) of zinc sulfide.

[for Zn, A_r = 65 for S, A_r = 32]

A student uses this apparatus to investigate the decomposition of hydrogen peroxide solution.

This is the equation for the reaction.

Give the test for oxygen.

Complete the dot‑and‑cross diagram for a molecule of hydrogen peroxide.

Show outer electrons only.

H O O H

The student measures the volume of oxygen collected at regular intervals until the reaction stops.

The table shows the student’s results.

Plot the student’s results on the grid.

Draw a curve of best fit.

Explain in terms of particle collision theory how decreasing the concentration affects the rate of a reaction.

The student repeats the experiment using the same volume of hydrogen peroxide solution but with half the original concentration.

All other conditions are kept the same.

On the grid, draw the curve you would expect the student to obtain.

In this reaction, the manganese(IV) oxide acts as a catalyst.

Explain how a catalyst works.

A student uses this apparatus to investigate the rate of reaction when hydrogen peroxide solution decomposes.

This is the equation for the reaction.

Give a reason why the gas that collects in the gas syringe is not pure oxygen.

The rate of reaction can be increased by adding a catalyst to the hydrogen peroxide solution.

Describe how a catalyst increases the rate of a reaction.

These solids catalyse the decomposition of hydrogen peroxide solution.

• lead(IV) oxide

• manganese(IV) oxide

Describe a method that the student could use to find out which solid is the more effective catalyst.

A student investigates the decomposition of a solution of hydrogen peroxide at different temperatures.

The graph shows how the total volume of oxygen collected in the syringe changes with time when the solution is at a temperature of 20 °C.

On the grid, draw the curve the student would obtain at a temperature of 40 °C when all other conditions are kept the same.

Zinc reacts with dilute hydrochloric acid to form zinc chloride and hydrogen gas.

This is the equation for the reaction.

In an experiment, 20 cm³ of hydrochloric acid containing 0.0036 mol are reacted with 1.3 g of zinc granules at a temperature of 30 °C.

Show by calculation that the zinc is in excess.

The volume of hydrogen collected is measured at regular time intervals.

Curve A shows the results of this experiment.

The experiment is repeated using 1.3 g of zinc powder instead of zinc granules.

All other conditions are kept the same.

On the grid, draw the curve you would expect to obtain.

In the original experiment, 20 cm³ of hydrochloric acid containing 0.0036 mol were reacted with 1.3 g of zinc granules at a temperature of 30 °C and curve A was obtained.

The student does two more experiments and obtains curves B and C.

In one of these experiments the student repeats the original method but at a temperature of 20 °C.

Explain in terms of particle collision theory why the curve obtained could be curve B.

In the other experiment the student repeats the original method but uses 20 cm³ of hydrochloric acid containing 0.0018 mol.

Explain why curve C shows the results the student obtained.

Catalysts can be used to speed up reactions.

Describe how a catalyst works.

A student investigates the effect of temperature on the rate of reaction between two solutions, A and B. When the reaction occurs, the mixture turns from colourless to blue.

This is the student’s method.

• pour 25 cm³ of solution A into a conical flask

• add solution B and measure the temperature of the mixture

• record the time taken for the mixture to turn blue

The student repeats this method at different temperatures.

Give two variables that the student needs to keep constant in this investigation.

The table shows the student’s results.

Plot the student’s results on the grid.

Draw a circle around the anomalous result.

Draw a curve of best fit.

Give a reason for the anomalous result.

Use your graph to determine the time taken for the mixture to turn blue at 55 °C.

Show your working on the graph.

Use information from the table to calculate the mean rate of reaction at 20 °C.

Use the expression

Give your answer in standard form.

Explain how increasing the temperature affects the rate of a reaction.

Refer to particle collision theory in your answer.

A student uses this apparatus to investigate the reaction between magnesium and dilute hydrochloric acid.

The word equation for the reaction is

magnesium + hydrochloric acid magnesium chloride + hydrogen

Complete the chemical equation for this reaction.

Give the test for hydrogen.

The student uses 0.090 g of magnesium and 0.025 mol of hydrochloric acid.

Show by calculation that the hydrochloric acid is in excess.

The student measures the volume of hydrogen collected at regular intervals until the reaction stops.

The table shows the student’s results.

Plot the student’s results.

Draw a curve of best fit.

Determine the volume of hydrogen collected in the first 10 seconds.

Show on the graph how you obtained your answer.

Explain why the rate of reaction is greatest at the start of the reaction.

The student repeats the experiment at a temperature 5 °C higher than the original temperature.

All other conditions are kept the same.

On the grid, draw the curve you would expect the student to obtain.

Explain, in terms of particle collision theory, how increasing the temperature affects the rate of reaction.

This question is about rates of reaction.

A student uses this method to investigate the rate of reaction between iron(III) nitrate solution and sodium thiosulfate solution.

• pour 50 cm³ of iron(III) nitrate solution into a conical flask

• add one drop of catalyst solution

• add 50 cm³ of sodium thiosulfate solution to the conical flask

• record the time for the mixture to become colourless

The student repeats the method using different catalysts and also with no catalyst.

The table shows the student’s results.

Explain which is the best catalyst for the reaction.

Explain how a catalyst increases the rate of a reaction.

The rate of a reaction can also be altered by changing the temperature or by changing the concentration of solutions.

Explain, using the particle collision theory, how increasing the temperature affects the rate of a reaction.

Explain why using a solution of a lower concentration decreases the rate of reaction.

A student uses this apparatus to investigate the rate of reaction between calcium carbonate chips and dilute hydrochloric acid.

Every 20 seconds the student records the reading on the balance.

Explain why using a cotton wool plug increases the accuracy of the student’s results.

Complete the equation for the reaction by adding the state symbols.

The student uses the balance readings to find the decrease in mass of the flask and contents.

The graph shows the student’s results.

Give a reason why there are some calcium carbonate chips remaining in the flask when the reaction stops.

State how the student would know when the reaction has stopped.

Use the graph to determine the amount, in moles, of carbon dioxide produced during the reaction.

[M_r of CO₂ = 44]

Use the graph to calculate the rate of reaction, in grams per second, at time 60 seconds.

Show your working on the graph.

The student repeats the investigation by diluting the original hydrochloric acid.

The student then determines the initial rate of reaction at different percentage concentrations of the original hydrochloric acid.

The graph shows the student’s results.

Describe the relationship between the initial rate of reaction and percentage concentration of the original hydrochloric acid.

Explain why changing the concentration of hydrochloric acid has an effect on the initial rate of reaction.

Zinc reacts with dilute hydrochloric acid to form hydrogen.

Give a chemical equation for this reaction.

Give a test for hydrogen gas.

A student investigates the reaction between pieces of zinc and dilute hydrochloric acid.

In each experiment, he uses the same mass of zinc but a different volume of the acid.

He collects the hydrogen and measures its volume in each experiment.

The graph shows the student’s results.

Volume of dilute hydrochloric acid in cm³

Use the graph to find the minimum volume of acid needed to react with all of the zinc.

The student repeats the investigation, using hydrochloric acid of double the original concentration.

Determine the volume of hydrogen that would be collected using 15 cm³ of this acid.

Show your working on the graph.

Explain how increasing the concentration of the hydrochloric acid affects the rate of reaction.

The rate of reaction could also be affected by changing the temperature of the hydrochloric acid, or by using a catalyst.

Explain one other way in which the rate of reaction between zinc and hydrochloric acid can be affected.

A solution of hydrogen peroxide decomposes when a catalyst of manganese(IV) oxide is added.

The products of the reaction are water and oxygen.

Complete the chemical equation for this reaction.

Give a test for oxygen.

State the reason for adding a catalyst.

A student investigates how changing the concentration of the hydrogen peroxide solution affects the rate of this reaction.

She uses this apparatus.

The student records the volume of oxygen that collects every 2 minutes for 16 minutes.

The table shows her results.

Plot the student’s results on the grid.

Draw a circle on the grid around the anomalous result.

Draw a curve of best fit through the points, ignoring the anomalous result.

Suggest a mistake that the student might have made to cause the anomalous result.

Determine the volume of oxygen collected during the first 3 minutes.

Show on your graph how you obtain your answer.

The student repeats the experiment using hydrogen peroxide solution of half the concentration of the original solution.

She keeps the volume of the hydrogen peroxide solution and all other conditions the same.

Draw on the grid the curve you would expect the student to obtain.

Explain how using hydrogen peroxide solution of half the concentration affects the rate of the reaction.

Refer to particle collision theory in your answer.

Dilute hydrochloric acid reacts with a solution of sodium thiosulfate (Na₂S₂O₃) to form a precipitate.

The equation for the reaction is

State the name of the precipitate that forms.

The reaction is often used to investigate rates of reaction.

The diagram shows the apparatus a student uses to investigate the effect of temperature on the rate of the reaction.

This is the student’s method.

● pour 50 cm³ of cold sodium thiosulfate solution into a conical flask and heat it to 20C

● draw a cross (X) on a piece of paper and place it under the flask

● add 5 cm³ of dilute hydrochloric acid to the flask

● look at the cross from above and record the time taken until the cross cannot be seen

The student repeats the experiment four times, using sodium thiosulfate solution at a different temperature each time.

He keeps the volumes of sodium thiosulfate solution and hydrochloric acid constant in each experiment.

Give two other factors that the student should keep constant.

The table shows the student’s results.

The highest temperature the student uses is 60C because he thinks the results might not be as accurate at temperatures higher than 60C.

Suggest a reason why the results might not be as accurate at temperatures higher than 60C.

The student wants to compare the rates of the reaction at the different temperatures.

He uses this formula to obtain a value for each rate of reaction

The table shows the value of the rate of reaction at each temperature.

Plot the values of temperature and rate of reaction on the grid.

Draw a curve of best fit through the points.

Use the graph to determine a value for the rate of the reaction at 45C.

Show on the graph how you obtained your answer.

Calculate the time that it would take for the cross not to be seen at 45C.

Describe the relationship between rate of reaction and temperature shown by the graph.

Explain, in terms of particle collision theory, the effect that increasing the temperature has on the rate of a reaction.

This question is about ethane and ethene.

Ethane can be obtained from crude oil.

Describe the industrial process used to separate crude oil into fractions.

The equation for the reaction between ethene gas and hydrogen gas is

The rate of this reaction can be increased by increasing the pressure.

Explain why increasing the pressure increases the rate of this reaction.

The rate of this reaction can also be increased by using a catalyst.

Explain how using a catalyst increases the rate of a reaction.

Give one other way that the rate of reaction between ethene gas and hydrogen gas can be increased.

The reaction between ethene and hydrogen is exothermic.

Complete the reaction profile diagram, including labels for the activation energy and the enthalpy change, H.

The reaction between ethene and hydrogen can be represented using displayed formulae.

H H H H

Use the bond energies in the table to calculate the enthalpy change, H, in kJ/mol for this reaction.

H =_........ kJ/mol