Unit 12 - Rates Of Reaction Flashcards
Describe an experiment to investigate the changes in surface area of a solid on the rate of a reaction
Put a set mass of magnesium in hydrochloric acid
Time the reaction
Change the from of magnesium keeping the mass the same (powder, wire, strips)
The more surface area (the smaller the pieces of magnesium) the faster the reaction. This is because there is more space for molecules to collide and a higher chance of high speed collisions
Describe an experiment to investigate the effects of changes in concentration of solutions in the rate of a reaction
Put a set mass of marble chips into dilute hydrochloric acid
Time the reaction
Change the ratio of water to hydrochloric acid
The more concentrated the hydrochloric acid (the lower the ratio of water) the faster the reaction. This is because the reactant particles become more crowded and there is a greater chance of the particles colliding with energy larger than or equal to the activation energy
Why does a higher gas pressure give a higher reaction rate
the reactant particles become more crowded and there is a greater chance of the particles colliding with energy larger than or equal to the activation energy
Describe an experiment to investigate the effects of Chang Erin temperature on reaction rate
Put a set mass of magnesium powder into a set mass of hydrochloric acid
time the reaction
Carry out this reaction at different temperatures
The higher the temperature the faster the rate because of the increase in the number of high energy collisions caused by the particles having more kinetic energy. It is only these collisions (possessing at least the activation energy for the reaction) which result in a reaction.
Describe the experiment to investigate the effects of the use of a catalyst on rate of reaction
If you have hydrogen peroxide it will not decompose
If you put it with manganese dioxide (catalyst) the H2O2 will decompose into water and oxygen
The manganese dioxide is unaltered by the reaction (same mass before and after)
The more of the catalyst the faster the reaction, this is because catalysts lower the activation energy needed therefore there are more collisions that are higher than or equal to the activation energy. Different reactions need different catalysts.
What is ‘activation energy’
The amount if energy required for a reaction to start happening
What is particle collision theory
Collision theory states that, for particles to react, they must:
- collide with enough energy to react
- collide in the right orientation to react
(the more frequent the collisions, the more likely these are)
What is a catalyst
A catalyst is a substance which alters the rate of a chemical reaction but is unchanged in mass and is unchanged chemically during the reaction. They do this by providing an alternative route of lower activation energy for the reaction this means that a greater proportion of collisions have the minimum energy needed to react (so the reaction rate is increased)
