Rates Of Reaction

Mean rate of reaction=quantity of reactant (or product)/
time taken

Factors that affect rate of reaction

• concentration
• pressure
• surface area
• temperature
• presence of catalyst

Increasing the conc,pressure and SA increases the frequency of collisions and so increases the rate of reaction.

Increasing the temp increases the frequency of collisions and makes the collisions more energetic and so incraeses the rate of reaction.

Collision Theory- explains how various factors affect rate of reaction, chemical reactions can occur only when reacting particles collide with each other and with sufficient energy

Catalyst- increase rate of reaction by providing alternative pathway for the reaction which has a lower activation theory. They are not used up.

Activation Energy- The minimum amount of energy needed that particles must have to react.

Exothermic reactions transfer energy to the surroundings. Endothermicreactions take in energy from the surroundings.

Reversible reactions are where the products can react to remake the originalreactants. If the forward reaction is exothermic, the reverse reaction is endothermic.

Exothermic Reactions

These are reactions that transfer energy to the surroundings. The energy is usually transferred as heat energy, causing the reaction mixture and its surroundings to become hotter. The temperature increase can be detected using a thermometer. Some examples of exothermic reactions are:

• burning
• neutralisation reactions between acids and alkalis
• the reaction between water and calcium oxide

Endothermic reactions

These are reactions that take in energy from the surroundings. The energy is usually transferred as heat energy, causing the reaction mixture and its surroundings to get colder. The temperature decrease can also be detected using a thermometer. Some examples of endothermic reactions are:

• electrolysis
• the reaction between ethanoic acid and sodium carbonate
• the thermal decomposition of calcium carbonate in a blast furnace