Chemistry - 8 Rates and Equilibrium - 8.1 Rate of Reaction & 8.2 Collision Theory and Surface Area & 8.3 The Effect of Temperature

Situations where controlling the rate of reaction is important [2]:

- in the body
- in the chemical industry

Rate of reaction can be how quickly [2]:

- reactants are used up
- products are made

When would decreasing mass be used to determine rate of reaction?

when the reaction gives off a gas

When would increasing volume of gas be used to determine rate of reaction?

when a reaction gives off a gas

When would increasing opacity be used to determine rate of reaction?

when a reaction forms a precipitate

Decreasing mass method [3]:

- add a known mass of reactants to a conical flask or beaker and place it on a scale
- use a stopwatch to record the mass at different set intervals
- plot mass of reacting mixture against time

Increasing volume of gas method [3]:

- place the reactants in a conical flask fitted with a gas syringe
- use a stopwatch to record the volume of gas at different set intervals
- plot volume of gas against time

Increasing opacity method [3]:

- place reactants in a beaker or flask above a light sensor and record light intensity before reaction
- use a stopwatch to record the light intensity at different set intervals
- plot light intensity against time

How to find a gradient from a curved graph:

draw a tangent and find its gradient

mean rate of reaction = [2]

- quantity of reactant used/time taken
- quantity of product formed/time taken

Collision theory

for a reaction to occur, particles must collide and collide with sufficient energy

Activation energy

minimum energy required to start a chemical reaction

The effect of surface area on rate of reaction [3]:

- as surface are increases, more particles are exposed to collisions
- more particles can react at once
- the rate of reaction increases

The effect of temperature on rate of reaction [4]

- as temperature increases, particles have increased kinetic energy, causing them to collide more frequently
- this also causes them to collide with more energy
- this results in more frequent successful collisions
- the rate of reaction increases