The Rate of Reaction in the Reaction Between Hydrochloric Acid and Sodium Thiosulphate

To see how the concentration of acid affects the rate of reaction in

the reaction between hydrochloric acid and sodium thiosulphate.

Planning;

Aim

To see how the concentration of acid affects the rate of reaction in

the reaction between hydrochloric acid and sodium thiosulphate.

Background;

All reactions occur because of the particles that make up the

reactants will collide, and if they have sufficient energy, react

forming or breaking bonds.

All four methods of increasing the rate of reaction can be explained

in terms of increasing the number of collisions.

Temperature increases the number of collisions. When the temperature

is increased, the particles all move quicker. If they're moving

quicker, they're going to have more collisions.

Reactions only happen if the particles collide with enough energy. At

a higher temperature there will be more particles colliding with

enough energy to make the reaction happen. This initial energy is

known as the activation energy, and it's needed to break the initial

bonds.

All reactions are exothermic in one direction and endothermic in the

other. If the temperature is raised, the endothermic reaction will

increase to use up the extra heat. If the temperature is reduced, the

exothermic reaction will increase to give out more heat.

The affect of temperature on rates of reaction is important. Raising

the temperature makes the rate of reaction faster. Because the

temperature increases, the pressure of the molecules increase, causing

them to move more faster which will then lead them to bump into each

other more frequently. Therefore the molecules are reacting.

Concentration increases the number of collisions. If the solution is

made more concentrated it means there are more particles of reactant

knocking about between the water molecules, which makes collisions

between the important particles more likely. In a gas, increasing the

pressure has the same effect as it means the molecules are more

squashed up together so there are going to be more collisions.

If one of the reactants is a solid then breaking it up into smaller

pieces will increase its surface area. This means the particles around

in the solution will have more area to work on so there'll be more

useful collisions. A catalyst works by giving the reacting particles a

surface to stick to where they can bump into each other. This

obviously increases the number of collisions too.

Catalysts lower the activation energy of reactions, making it easier

for them to happen. This means that any of the other variables that

affect the rate of reaction can be lowered.

An enzyme is a biological catalyst, which increases the rate of

reaction. Enzymes are naturally occurring catalysts responsible for

many essential biochemical reactions. Caseous and liquid catalysts are