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Year 10
OCR
Higher

Concentration and rate: analysis

I can represent graphically and explain how the rate of reaction depends on the concentration of one of the reactants.

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New
New
Year 10
OCR
Higher

Concentration and rate: analysis

I can represent graphically and explain how the rate of reaction depends on the concentration of one of the reactants.

Download all resources
Share activities with pupils

Lesson details

Key learning points

  1. The changing rate of a chemical reaction can be represented by a graph of volume of gas produced against time.
  2. When reacting excess acid, the same volume of gas is produced for equal amounts of magnesium.
  3. Doubling the concentration doubles the rate of reaction.
  4. The gradient of a rate of reaction graph can be calculated from a tangent drawn at a point on the curve.

Common misconception

Thinking that as the concentration of a solution in excess changes, so does the volume of gas produced.

The slide deck uses graphical data to show that the same volume of gas is produced when different concentrations are used, so long as the reacting solution is in excess.

Keywords

  • Gradient - The gradient on a graph represents the rate at which one quantity changes relative to another.

  • Rate of reaction - Rate of reaction is the speed with which a chemical reaction takes place.

  • Excess - A reactant in excess is present in a greater amount than is necessary to completely react with the limiting reactant.

  • Mean rate of reaction - The mean rate of reaction is the average rate at which reactants are converted into products in a given time.

  • Tangent - A tangent is a straight line that touches a curve at exactly one point without crossing it.

If students have collected data from an investigation on the effect of concentration on rate of reaction, they could use their own data to plot graphs and calculate the mean and instantaneous rate of reaction.
Teacher tip

Equipment

Graph paper, ruler (to draw tangent) and calculator.

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.
How does increasing the concentration of reactants affect the rate of reaction?
It decreases the frequency of collisions.
Correct answer: It increases the frequency of collisions.
It has no effect on the rate of reaction.
It decreases the energy of collisions.
Q2.
Which of the following will not increase the rate of reaction?
increasing the concentration of reactants
increasing the surface area of solid reactants
Correct answer: decreasing the temperature
increasing the pressure of reacting gases
Q3.
In the collision theory, what does "successful collision" mean?
any collision between reactant particles
Correct answer: a collision that results in a reaction
a collision that increases the energy of particles
a collision with no change in particles
Q4.
What is the purpose of drawing a tangent to the curve on a rate of reaction graph?
to find the total volume of gas produced
to determine the average rate of reaction
Correct answer: to find the instantaneous rate of reaction at a specific time
to measure the concentration of reactants
Q5.
What does a flat horizontal line on a graph of volume against time indicate?
The reaction is occurring rapidly.
Correct answer: The reaction has stopped.
The reaction is occurring slowly.
The reaction rate is increasing.
Q6.
For most reactions, when is the rate of reaction highest?
Correct answer: at the start
in the middle
towards the end
when the reaction has reached completion

Exit quiz

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6 Questions

Q1.
What does the gradient of the line on a graph of volume of gas produced against time represent?
total volume of gas produced
Correct answer: rate of reaction
time taken for reaction
concentration of reactants
Q2.
When plotting a graph of the volume of gas produced against time, how would the graph change if the concentration of the reacting solution is increased?
The graph would be less steep.
Correct answer: The graph would be steeper.
The graph would not change.
The graph would be a constant horizontal line.
Q3.
What happens to the rate of reaction when the concentration of reactants is doubled?
It stays the same.
It halves.
Correct answer: It doubles.
It quadruples.
Q4.
How can the gradient of the curved section on a rate of reaction graph be determined at a specific point?
by calculating the area under the curve
by drawing a horizontal line
Correct answer: by drawing a tangent to the curve at that point
by measuring the distance between two points on the curve
Q5.
If you use the same mass of magnesium and react it with different concentrations of excess acid, how will this affect the volume of gas produced?
Different volumes of gas will be produced for different concentrations of acid.
Correct answer: The same volume of gas will be produced for different concentrations of acid.
No gas will be produced for high concentrations of acid.
Higher concentrations will produce higher volumes of gas.
Q6.
If two experiments produce the same volume of gas but one reaction takes less time to complete, what can you say about the concentration of reactants?
Correct answer: The reaction that took less time had a higher concentration of reactants.
Both reactions had the same concentration.
The reaction that took more time had a higher concentration of reactants.
Concentration does not affect reaction rate.