Rates of Reaction

What is a Rate of Reaction? (ROR)

Measuring Reaction Rates

Different reactions can happen at different rates.

Reactions that happen slowly have ……………………………………………………………………………

Reactions that happen quickly have ……………………………………………………………………………

For example;

The chemical weathering of rocks is a ......

Explosions are very fast reactions: they have ……………………………………………………….

Reactants and products

There are three ways to measure the rate of a reaction:

We can use an equation the measure the rate of reaction:

Questions

  1. What is the rate of reaction if 24cm3 of hydrogen gas is produced in two minutes?
  1. What is the rate of reaction if 55cm3 of carbon dioxide gas is produced in 5 minutes?
  1. What is the rate of reaction 3.4g of copper sulphate was produced in 3 days?

Drawing Graphs

Questions

  1. 5g of marble chips were added to 100 cm3 of 1M hydrochloric acid. The chips dissolved, producing carbon dioxide gas. The loss in mass of the chips was measured. Here is a table of results.

Time (mins) / 0 / 2 / 4 / 6 / 8 / 10 / 12 / 14 / 16
Loss of mass (g) / 0 / 2.1 / 3.0 / 3.1 / 3.6 / 3.8 / 4.0 / 4.0 / 4.0
  1. Using the graph paper provided, plot a graph of the results. Join the points with a smooth curve (4 marks).

  1. On the same graph , sketch the curve you would expect to see if 5g of marble powder was used in the experiment instead (2 marks)

The rate of reaction depends on 4 things:

The Effect of Temperature on Rates

What is the effect of changing the temperature on the rate of the reaction?

1. Sketch a graph to show how the rate of reaction is affected by temperature. (Label axis)

  1. Explain why vegetables last longer in a fridge (2 marks)
  1. What would happen to a reaction if the temperature was lowered? (3 marks)

Draw the effect that temperature has on the rate of reaction according to the collision theory.

The Effect of a Catalyst on Rates

What is a catalyst?

What effect does a catalyst have on the rate of a reaction?

Sketch a graph to show how the rate of reaction is affected by catalysts. (Label axis)

The Effect Surface Area on Rates

What effect does surface area have on the rate of the reaction?

Collision Theory and Surface Area

Sketch a graph to show how the rate of reaction is affected by surface area. (Label axis)

  1. Explain why potatoes cook faster if they are cut into small pieces. (2 marks)

The Effect of Concentration/Pressure on Rates

Collision Theory and Concentration

Sketch a graph to show how the rate of reaction is affected by concentration. (Label axis)

  1. What would happen to the rate of the reaction between magnesium chips and hydrochloric acid if the concentration of the hydrochloric acid concentration was doubled? (2 marks)