Rates of Reaction

Rates of Reaction

Coursework

Aim

The aim of this investigation is to find out and observe how temperature affects the rate of reaction. I am going to investigate the changes caused to the solution of hydrochloric acid and sodium thiosulphate when the temperature is changed.

Hypothesis

I know that temperature is a major factor in this as increasing or decreasing the temperature changes the movement of particles in a substance therefore changing the rate of reaction. When a reaction mixture is heated up, each particle in it acquires more energy and collides more with other particles.

Therefore, from my own knowledge, I can make the prediction that if you increase the temperature of a particular reaction, you increase the speed at which it takes place. This is simply because the particles carry more energy and collide more often where these collisions contain enough energy to break the energy barrier. Collisions between particles are useless unless they break the energy barrier and this is exactly what increasing the temperature will allow them to do.

Apparatus

The equipment I need to carry out the work and to obtain my results is:

• Sodium thiosulphate solution

• Hydrochloric acid

• 250cmі conical flask

• Thermometer

• 50cmі measuring cylinder

• 10cmі measuring cylinder

• Water bath

• Stop watch

• A pair of Tongs

• Paper marked with an X

Diagram

Safety Precautions

Throughout this experiment, I made sure that safety was one of my top priorities. I wore goggles at all times to protect my eyes and took off my blazer and tie so they didn’t accidentally get caught in a bunsen burner. I used tongs to make sure I didn’t touch the water bath.

Method

Firstly, I measured 50cm sodium thiosulphate solution using the conical flask and put it into the water bath which was pre-heated to the appropriate temperature. The appropriate temperature was checked using the thermometer. I now placed the paper with the X marked on it beneath the flask in the water bath. At the appropriate temperature, 5cm hydrochloric acid was measured using the measuring cylinders and then added to the flask containing the sodium thiosulphate.

The stop clock was started immediately to make results more accurate and I recorded the time in seconds for the cross to disappear. I carried this out from 30 C to 70 C. I repeated each temperature 2 times to make my results accurate and calculated an average.

Observation

All rate of reaction experiments have visible results and this experiment is no exception. When I added the hydrochloric acid to the flask I observed immediately at each temperature to see the changes or reactions that were taking place between the particles.

When observing the experiment, the changes I saw take place was the colour of the sodium thiosulphate and hydrochloric acid solution. At the initial temperatures, which were quite low, the solution became very foggy and misty but only after a fairly long time. At the higher temperatures, the solution became foggy very quickly and in both cases, the solution continued to get foggy until it was no longer clear. I could not see through the solution at all. The colour of the solution went from a clear colourless liquid to a greyish-green colour and at the higher temperatures, the colour changed almost immediately. I did not see any gas given off in the actual reaction. The change in colour was smooth and there was no sound made when it happened.

Fair Test

To make my experiment a fair one, I had to look at a lot of things. Firstly, I looked at the factors that may have affected how well the investigation would work and these were things like doing the actual experiment in different conditions or using different equipment e.g. bunsen burner instead of water bath. To prevent this, I made sure that