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Year 10
OCR
Foundation

Evaluating methods for measuring the rate of reaction

I can compare different methods for measuring the effect of concentration on the rate of reaction and suggest improvements.

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New
New
Year 10
OCR
Foundation

Evaluating methods for measuring the rate of reaction

I can compare different methods for measuring the effect of concentration on the rate of reaction and suggest improvements.

Download all resources
Share activities with pupils

Lesson details

Key learning points

  1. Measuring volume of gas produced throughout a reaction allows the changing rate of reaction to be calculated.
  2. Errors in measuring volumes of gas over time include timing, reading volumes in real time and gas displaced by the bung.
  3. Measuring an end-point in a reaction allows direct and simple comparison of reaction rates.
  4. Errors in measuring end-points include subjectivity of observations, measuring times and volumes, and contamination.

Common misconception

Adding a bung to the top of a conical flask does not affect volume measurements.

The bung can displace a small volume of gas, which can affect the accuracy of the measurements. It is essential to account for the volume displaced by the bung in calculations.

Keywords

  • Accuracy - Accuracy refers to how close a measured value is to the true or standard value.

  • Repeatable - A method is described as repeatable if a person uses the same method and obtains the same/similar results when repeating the experiment.

  • Parallax error - A parallax error occurs when a measurement is not taken at eye-level.

  • Systematic error - A systematic error is caused by the equipment used.

Demonstrate the apparatus set-up to help students understand where gas can escape to the surroundings and that the bung displaces gas from the conical flask.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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Starter quiz

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6 Questions

Q1.
Which method would be most suitable for measuring the rate of a reaction that produces a gas as one of its products?
end-point method
Correct answer: gas collection method
titration method
combustion method
Q2.
How can we measure the amount of gas produced in a chemical reaction?
Correct answer: using an inverted measuring cylinder
using a stopwatch
Correct answer: using a gas syringe
using a burette
using a conical flask
Q3.
Typically what happens to the rate of reaction during a reaction?
the rate of reaction increases
Correct answer: the rate of reaction decreases
the rate of reaction remains at zero
the rate of reaction remains constant
Q4.
When measuring the volume of gas produced in a chemical reaction, what effect will gas escaping to the surroundings have on the results?
The measured volume of gas produced will be higher than the true value.
Correct answer: The measured volume of gas produced will be lower than the true value.
There will be no effect on the volume of gas recorded.
Q5.
How can we calculate the instantaneous rate of reaction from a volume of gas produced versus time graph?
calculating the area under the graph
reading the maximum amount of gas produced
measuring how long the reaction took to reach completion
Correct answer: calculating the gradient at specific points
Q6.
Match the type of error to the correct definition.
Correct Answer:zero error,occurs when an instrument does not reset to zero

occurs when an instrument does not reset to zero

Correct Answer:systematic error,is caused by the equipment used

is caused by the equipment used

Correct Answer:parallax error,occurs when a measurement is not taken at eye-level

occurs when a measurement is not taken at eye-level

Correct Answer:random error,made by the investigator such as timing incorrectly

made by the investigator such as timing incorrectly

Exit quiz

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6 Questions

Q1.
What is a potential error that could affect the accuracy of end-point measurements?
Correct answer: contamination
colour changes
bubbling
a temperature change
Q2.
What type of error could affect the accuracy of measuring the volume of gas over time?
Correct answer: timing errors
colour changes
pH measurement errors
temperature changes
Q3.
Which apparatus set-up can cause errors when measuring volumes of gas produced?
incorrect temperature
Correct answer: gas displaced by the bung
incorrect pH
an inverted measuring cylinder
Q4.
Why is measuring an end-point in a reaction useful?
Correct answer: It allows direct and simple comparison of reaction rates.
It changes the temperature of the reaction.
It alters the reactants used.
It measures the pH of the solution.
Q5.
How can you reduce subjectivity in observing the end-point of a reaction?
Correct answer: using automated sensors such as light sensors
rely on human judgement
get a different person to take each reading
ignore observations
change the reactants
Q6.
Which key term is used for results that are close to the true or standard value?
Correct answer: accurate
precise
repeatable
reproducible