Collision theory and activation energy

When solutions P and Q are mixed together, a purple mixture forms. This mixture slowly becomes colourless.

A student pours 25 cm³ of solution P into a conical flask and then adds 25 cm³ of solution Q.

The student uses a beaker to measure out these volumes.

Name a piece of apparatus that could be used to measure these volumes more accurately.

The student investigates this reaction using the apparatus shown in Figure 12. The student measures the time taken for the cross to become visible. The experiment is repeated at different temperatures.

Figure 13 shows the results.

The concentrations of the solutions are kept constant in each experiment.

State one other variable that should be kept constant.

State, and explain in terms of particles, how the time taken for the cross to become visible would change if a temperature of 80 °C was used.

The concentration of solution Q is 26.8 g dm^–3.

Calculate the mass of solid Q present in 25 cm³ of solution Q.

The student repeats the experiment at 20 °C, with the addition of a catalyst.

Explain how the addition of a catalyst will affect the rate of reaction.

Hydrogen peroxide, H₂O₂, decomposes into oxygen and water.

A catalyst can be used to increase the rate of this reaction.

Use a word or phrase from the box to complete the sentence about the mass of the catalyst in a reaction.

During a reaction, the mass of a catalyst_........ .

Complete the balanced equation for this reaction and add the missing state symbol.

When solutions P and Q are mixed together, a purple mixture forms. This mixture slowly becomes colourless.

A student pours 25 cm³ of solution P into a conical flask and then adds 25 cm³ of solution Q.

The student uses a beaker to measure out these volumes.

Name a piece of apparatus that could be used to measure these volumes more accurately.

The student investigates this reaction using the apparatus shown in Figure 3. The student measures the time taken for the cross to become visible. The experiment is repeated at different temperatures.

Figure 4 shows the results.

The concentrations of the solutions are kept constant in each experiment.

State one other variable that should be kept constant.

State, and explain in terms of particles, how the time taken for the cross to become visible would change if a temperature of 80 °C was used.

The concentration of solution Q is 26.8 g dm^–3.

Calculate the mass of solid Q present in 25 cm³ of solution Q.

The student repeats the experiment at 20 °C, with the addition of a catalyst.

Explain how the addition of a catalyst will affect the rate of reaction.

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

The student measures the total volume of carbon dioxide gas produced each minute, for 10 minutes.

Figure 14 shows part of the apparatus used in the experiment.

Complete Figure 14 by drawing and labelling apparatus that could be used to collect and measure the volume of the carbon dioxide gas.

Figure 15 shows a graph of the results of the experiment.

A tangent has been drawn on the curve at a time of 3.5 minutes.

State the total volume of carbon dioxide produced in the first 3.5 minutes.

Using the tangent, calculate the rate of reaction at 3.5 minutes in cm³ per minute.

rate =_........ cm³ per minute

The student repeats the experiment using the same mass of smaller marble chips.

All other conditions remain the same.

Explain the effect on the rate of reaction of using smaller marble chips.

Which change would make the rate of reaction slower?

In this experiment the volume of carbon dioxide gas produced is measured.

Give a different way that the amount of carbon dioxide produced can be measured.

In this experiment there is an excess of dilute hydrochloric acid.

State what you would see in the conical flask at the end of the experiment.

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

The student measures the total volume of carbon dioxide gas produced each minute, for 10 minutes.

Figure 3 shows part of the apparatus used in the experiment.

Complete Figure 3 by drawing and labelling apparatus that could be used to collect and measure the volume of the carbon dioxide gas.

Figure 4 shows a graph of the results of the experiment.

A tangent has been drawn on the curve at a time of 3.5 minutes.

State the total volume of carbon dioxide produced in the first 3.5 minutes.

Using the tangent, calculate the rate of reaction at 3.5 minutes in cm³ per minute.

rate =_........ cm³ per minute

The student repeats the experiment using the same mass of smaller marble chips.

All other conditions remain the same.

Explain the effect on the rate of reaction of using smaller marble chips.

Which change would make the rate of reaction slower?

A student used the apparatus shown in Figure 3 to investigate the reaction between marble chips and dilute hydrochloric acid.

The student recorded the volume of gas every minute as shown in Figure 4.

On the grid, plot the results shown in Figure 4.

Draw a curve of best fit.

Rate of reaction can be calculated using

Figure 5 shows the rates of reaction calculated from the results of this experiment.

The rate of reaction for the time interval 2 to 3 minutes is missing.

Calculate the rate of reaction for the time interval 2 to 3 minutes.

rate of reaction =_........ cm³min

State and explain what happens to the rate of reaction as the acid reacts with the marble chips in this experiment.

The student repeated the experiment using the same volume of acid and the same mass of marble chips but used smaller marble chips.

All other conditions remained the same.

The student found that the reaction with the smaller marble chips was faster to start with but produced the same volume of gas.

Using this information, draw a line on the grid to show the results for the reaction with the smaller marble chips.

Label this line ‘C’.

A student used the apparatus in Figure 13 to investigate the rate of the reaction between a metal and dilute hydrochloric acid.

Pieces of the metal were placed in dilute hydrochloric acid in the flask, and the total volume of gas produced was measured every minute.

Figure 14 shows a graph of the student’s results.

Name a piece of apparatus that would be better to measure the volume of gas produced, instead of the 250 cm³ measuring cylinder.

Give a reason for your answer.

name of apparatus

reason

Calculate the mean rate of production of hydrogen over the first 90 seconds, in cm³ per second.

rate =_........ cm³ per second

The student measured the volume of gas for 10 minutes.

State why the measurements could have been stopped at 9 minutes.

The experiment was repeated, but with acid of a higher concentration.

The rate of reaction was faster.

Explain why the rate of reaction increases when the concentration of acid is increased.

Another student suggests four other ways of increasing the rate of this reaction.

Which one is correct?

The apparatus in Figure 13 can be used to measure the rate of the reaction between marble chips and hydrochloric acid.

The student needs different sized marble chips.

Describe how the student can make small and medium sized marble chips from large chips.

A student used the apparatus in Figure 3 to investigate the rate of the reaction between a metal and dilute hydrochloric acid.

Pieces of the metal were placed in dilute hydrochloric acid in the flask, and the total volume of gas produced was measured every minute.

Figure 4 shows a graph of the student’s results.

Name a piece of apparatus that would be better to measure the volume of gas produced, instead of the 250 cm³ measuring cylinder.

Give a reason for your answer.

name of apparatus

reason

Calculate the mean rate of production of hydrogen over the first 90 seconds, in cm³ per second.

rate =_........ cm³ per second

The student measured the volume of gas for 10 minutes.

State why the measurements could have been stopped at 9 minutes.

The experiment was repeated, but with acid of a higher concentration.

The rate of reaction was faster.

Explain why the rate of reaction increases when the concentration of acid is increased.

Another student suggests four other ways of increasing the rate of this reaction.

Which one is correct?

Magnesium reacts with dilute sulfuric acid to form magnesium sulfate and hydrogen gas.

A student wants to find out the effect of temperature on the rate of this reaction.

The student used the following method.

step 1pour 25 cm³ of dilute sulfuric acid into a conical flask step 2 warm the acid until its temperature is 30 °C step 3 add a piece of magnesium to the acid step 4 start a stopwatch step 5 wait until the reaction has finished step 6 stop the stopwatch step 7 repeat steps 1–6 but at 50 °C.

The student kept the volume of sulfuric acid the same when they repeated the method at 50 °C.

State two other variables that should be kept the same.

Which piece of equipment can be used to find the volume of 25 cm³ of sulfuric acid?

State how the student will know that the reaction has finished.

The reaction at 50 °C was faster than the reaction at 30 °C.

Give one reason, in terms of particles, why the reaction at 50 °C was faster than the reaction at 30C.

At 50 °C, 15.0 cm³ of gas was produced during the first 60 seconds of the reaction.

Calculate the average rate of reaction, in cm³ s^–1, for the first 60 seconds of the reaction.

average rate of reaction =_........ cm³

This question is about the rate of reaction between calcium carbonate and dilute hydrochloric acid.

The word equation for this reaction is

calcium carbonate + hydrochloric acid calcium chloride + water + carbon dioxide

Which of the following is the formula for calcium carbonate?

Some pieces of calcium carbonate were added to dilute hydrochloric acid in a conical flask and the volume of carbon dioxide produced was measured.

Complete the diagram in Figure 7 to show the apparatus to collect the gas produced and measure its volume.

The reaction between calcium carbonate and dilute hydrochloric acid was investigated at different temperatures.

State what could be used to keep the temperature of the conical flask and its contents at a temperature of 45 °C throughout the reaction.

Figure 8 shows a graph of volume of gas collected in this investigation.

Draw a tangent at 100 seconds on Figure 8. Use this tangent to calculate the rate of reaction at this time.

rate of reaction =_........ cm³

The temperature of the acid was kept at 45 °C.

State one other variable that needs to be controlled during this investigation.

Explain, in terms of particles, how decreasing the temperature affects the rate of this reaction.

Calcium carbonate reacts with dilute hydrochloric acid to produce carbon dioxide gas.

The rate of reaction between calcium carbonate and dilute hydrochloric acid at room temperature was investigated.

The investigation was carried out with different sized calcium carbonate pieces.

The mass of calcium carbonate and all other conditions were kept the same.

The results are shown in Figure 15.

State, using the information in Figure 15, the effect of the surface area of the calcium carbonate on the rate of this reaction.

The calcium carbonate powder produced 90 cm³ of carbon dioxide in five minutes.

Calculate the average rate of reaction in cm³s^–1.

The experiments were repeated at a higher temperature. The rate of reaction for each experiment increased.

Explain, in terms of particles, why the rate of reaction increased when the temperature was increased.

*(b) Zinc metal reacts with dilute hydrochloric acid to produce hydrogen gas.

zinc + hydrochloric acid zinc chloride + hydrogen

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

The student made the following prediction.

Devise a plan, including the apparatus you would use, to test the student’s prediction.

You are provided with pieces of zinc and two bottles of dilute hydrochloric acid. One bottle of hydrochloric acid is double the concentration of the other.

Calcium carbonate reacts with dilute hydrochloric acid to produce carbon dioxide gas.

The rate of reaction between calcium carbonate and dilute hydrochloric acid at room temperature was investigated.

The investigation was carried out with different sized calcium carbonate pieces.

The mass of calcium carbonate and all other conditions were kept the same.

The results are shown in Figure 1.

State, using the information in Figure 1, the effect of the surface area of the calcium carbonate on the rate of this reaction.

The calcium carbonate powder produced 90 cm³ of carbon dioxide in five minutes.

Calculate the average rate of reaction in cm³s^–1.

The experiments were repeated at a higher temperature. The rate of reaction for each experiment increased.

Explain, in terms of particles, why the rate of reaction increased when the temperature was increased.

The word equation for the reaction between magnesium and dilute hydrochloric acid is

magnesium + hydrochloric acid magnesium chloride + hydrogen

The reaction was carried out using the apparatus shown in Figure 11.

A strip of magnesium ribbon was placed in the conical flask. 100 cm³ of dilute hydrochloric acid was added to the conical flask.

The mass of the flask and contents was measured at regular intervals. The loss in mass was calculated. Figure 12 shows a graph of the results.

Name the apparatus that could be used to measure out 100 cm³ of dilute hydrochloric acid.

Explain why there is a loss in mass of the flask and contents.

The graph shows that the rate of reaction slows as the reaction takes place.

Explain, in terms of particles, why the rate of reaction between magnesium ribbon and dilute hydrochloric acid slows as the reaction takes place.

The experiment was repeated using the acid at a higher temperature. All other conditions were kept the same.

State the effect of the higher temperature on the mass loss after two minutes.

The original experiment was repeated using the same mass of magnesium powder instead of the magnesium ribbon. All other conditions were kept the same.

Sketch, on the graph in Figure 12, the line you would expect for this experiment.

Some reactions are affected by the presence of a catalyst.

State the effect of a catalyst on a reaction.

Devise a simple experiment to find out what happens to the mass of a solid catalyst during a reaction.

Calcium carbonate reacts with dilute hydrochloric acid to produce calcium chloride, water and carbon dioxide.

A student wanted to measure the amount of gas produced in two minutes.

The student suggested that this could be done by counting the number of bubbles formed. However, the bubbles are produced too quickly to count them.

Figure 4 shows a conical flask in which the calcium carbonate and dilute hydrochloric acid are reacting.

Complete Figure 4 to show the apparatus that could be used to measure accurately the volume of gas given off in two minutes.

The reaction between calcium carbonate and dilute hydrochloric acid is exothermic.

Explain, in terms of bond breaking and bond making, why some reactions are exothermic.

*(c) An investigation was carried out into the rate of reaction of calcium carbonate with dilute hydrochloric acid.

5.0g of small lumps of calcium carbonate were reacted with 50 cm³ of 0.50 mol dm^–3 hydrochloric acid. Another 5.0 g of the same sized lumps of calcium carbonate were reacted with 50cm³ of 1.0 mol dm^–3 hydrochloric acid. The volume of gas collected in two minutes was recorded for each experiment.

The two experiments were then repeated, each using 5.0 g of large lumps of calcium carbonate.

Figure 5 shows the results.

Explain, in terms of collision of particles, how these results show the effect of the size of the lumps of calcium carbonate and the effect of the concentration of the acid on the rate of this reaction.

(a) The rate of reaction between magnesium ribbon and dilute hydrochloric acid at room temperature is investigated.

The apparatus used is shown in Figure 11.

The volume of hydrogen gas given off was measured at regular intervals during the reaction.

The graph in Figure 12 shows the results of this experiment.

State a change that can be made to the apparatus in Figure 11 to measure the volumes of gas more accurately.

A tangent has been drawn to the line on the graph in Figure 12.

Calculate the rate of reaction at this point.

On the graph in Figure 12, draw the line you would expect to obtain if the magnesium ribbon in this experiment was replaced with an equal mass of powdered magnesium. All other conditions are kept the same.

The balanced equation for this reaction is

In another experiment, 0.1 moles of hydrochloric acid, HC l, were reacted with 0.1 g of magnesium ribbon.

Calculate the number of moles of magnesium, Mg, in the 0.1 g sample of magnesium ribbon. (relative atomic mass: Mg = 24)

In a further experiment, 0.5 mol of hydrochloric acid, HC l, were mixed with 0.5 mol of magnesium, Mg.

Use the equation to show that, in this experiment, the magnesium is in excess.

*(c) Two substances, A and B, each form a colourless solution. If the solutions are mixed in a beaker, A and B react to form a coloured product. The rate of the reaction between A and B can be investigated by placing the beaker containing the mixture on a cross on a piece of paper and timing how long it takes for enough coloured product to be produced to make the cross invisible when viewed from above, through the solution.

Use the results of these experiments to explain, in terms of the behaviour of particles, the effect of changing temperature and the effect of changing the concentration of A in solution on the rate of this reaction.