Rates of Reaction

Rates of Reaction Coursework.

Introduction.

In this piece of science coursework I will be experimenting how the

rate of reaction between Sodium thiosulphate and hydrochloric acid is

affected by the concentration of Sodium thiosulphate. I will measure

the rate of reaction by mixing the different quantities of Sodium

thiosulphate (50 - 10cm³) with a fixed quantity (5cm³) of hydrochloric

acid in a Conical flask and placing the flask on top of a white sheet

of paper with a cross clearly marked on it. I will then measure how

long it takes for a chemical reaction to take place. The time might

vary depending on the concentration of Sodium thiosulphate. I will do

this by timing how long it takes for the cross to disappear. I will be

measuring the quantity of sodium thiosulphate and hydrochloric acid I

use, by using a ‘pipette’ and a measuring cylinder, which will allow

me to precisely conduct my measurements.

I will make sure that my experiment is fair by using a different

measuring tube and pipette for each chemical.

Prediction.

I think that the rate of reaction between sodium thiosulphate and

hydrochloric acid will increase as the concentration of the sodium

thiosulphate solution increases. I state this because by increasing

the concentration you’re also increasing the amount of particles in

the solution. If there are greater amount particles then there will

be greater number collisions taking place and so the rate of reaction

increases as well as the temperature. The collision theory explains us

that if a chemical reaction is to take place, the particles in a

substance have to collide into each other with enough energy to break

bonds and hence to form new bonds. In a successful reaction particles

need to collide with enough energy to form new bonds and this releases

energy, this is known as exothermic because energy is being released

into the surroundings.

Scientific Information.

The rate of a reaction is affected by four factors. The four factors

are:

Catalysts, Concentration, Surface Area and Temperature

· Temperature raises the amount of collisions between particles

because it causes the particles to move around more rapidly , and if

they’re moving around more quickly they will collide more often.

· Surface area raises the amount of collisions because if you split a

reactant up into smaller pieces then you will be expanding its surface

area. This means that the particles which are around the reactant will

have more surface area to work on, and this means that there will be

greater amount of successful collisions per second.

· An increase in concentration increases the amount of collisions

between particles because it means that there are greater amount of