Reaction Rates Worksheet

Name:……………………………………………………. Date: ……………………

Reaction RatesWorksheet
This worksheet accompaniesMeasuring Reaction RatesSummary,

Changing Reaction RatesSummaryand CatalystsSummary.

1. A student reacted marble chips with hydrochloric acid and measured the mass of the

flask and contents every 30 seconds using the apparatus shown.

He plotted the result on the graph below.

a) Draw a line of best fit on the graph.

b) What was the mass of the flask and contents after:

i) 2 minutes ……………………...

ii) 3 minutes …………………...…

iii) 4 minutes ………………….….

c) Predict the mass of the flask and contents after 11 minutes.

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d) Explain the shape of the curve using collision theory.

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2. Two students carried out a simple experiment to investigate the effect of concentration

on the rate of the reaction between magnesium powder and hydrochloric acid.

They decided to time how long it took to collect a tube full of gas using the

equipment shown below.

Their results were:

Concentration (mol/dm3) / 4 / 2 / 1 / 0.5 / 0.25
Time (s) / 3 / 6 / 13 / 25 / 37

a) Answer the following questions about the variables involved in this experiment.

i) Which is the dependent variable?......

ii) Which is the independent variable? ......

iii) Identify two control variables. ......

iv)Explain howthe variables you identified in part iii) could be controlled.

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b) Draw a graph of the results.

i) Describe the relationship your graph shows.

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ii) Identify an anomalous result ………………………………………………………….

iii) The students decided to repeat their measurements. This would improve the

□ accuracy □ reliability □ precision

iv) The students found the anomalous result gave the same reading as the first time.

Using collision theory, suggest a reason why this point does not lie on the line of best

fit. What could the students do to avoid this?

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c) You have been asked to review the method used in this experiment.

i) Do you feel their experiment was valid? Explain your answer.

ii) Identify the main source of error in the experiment.

iii) Explain how you could modify the experimental procedure to avoid this error.

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3. Below is a graph showing the rate of decomposition of hydrogen peroxide in an

experiment using a catalyst.

a) Add a line to the graph estimating the volume of oxygen produced if a more

effective catalyst were used. Label this line‘A’.

b) Add a line to the graph estimating the volume of oxygen produced if the

original catalyst were used at a lower temperature. Label thisline ‘B’.

c) Using collision theory, explain how a catalyst speeds up a reaction.

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d) Using collision theory, explain why a powdered catalyst is more effective than

a catalyst made up of large lumps.

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