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

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

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

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

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

Concentration and rate: analysis

Combined science

In the Industrial Chemistry unit, pupils will build on their knowledge of reaction rates to learn about the industrial processes involving chemical reactions and the factors that affect them.

In the Energy Changes in Reactions unit, pupils learned about bond breaking, bond making, and reaction profiles.

Rate of reaction

What does the gradient of the line on a graph of volume of gas produced against time represent?

The graph would be a constant horizontal line.

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?

What happens to the rate of reaction when the concentration of reactants is doubled?

by drawing a tangent to the curve at that point

by measuring the distance between two points on the curve

How can the gradient of the curved section on a rate of reaction graph be determined at a specific point?

Different volumes of gas will be produced for different concentrations of acid.

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.

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?

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.

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?

It decreases the frequency of collisions.

It increases the frequency of collisions.

It has no effect on the rate of reaction.

How does increasing the concentration of reactants affect the rate of reaction?

increasing the concentration of reactants

increasing the surface area of solid reactants

increasing the pressure of reacting gases

Which of the following will **not** increase the rate of reaction?

a collision that increases the energy of particles

In the collision theory, what does "successful collision" mean?

to determine the average rate of reaction

to find the instantaneous rate of reaction at a specific time

to measure the concentration of reactants

What is the purpose of drawing a tangent to the curve on a rate of reaction graph?

What does a flat horizontal line on a graph of volume against time indicate?

For most reactions, when is the rate of reaction highest?

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