Increasing the surface area of a solid, will increase the rate of reaction. The reaction will only take place at the surface of a solid. This means that the particles within the solid can’t react, until those on the surface have reacted and moved away. Magnesium powder has a greater surface area then lumps of Magnesium so there will be more successful collisions.
Increasing the pressure on the reaction between gases will increase the rate of reaction. By doing this the particles will move closer. The closer the particles are there will be more collisions.
Increasing the intensity of light will increase the arte of some reactions. As some reactions are increased by light. Light has the same effect as increasing temperature.
A catalyst also increases the rate of reaction. It is a substance that speeds or sometimes slows down the rate of reaction, without being used up itself. Catalysts work by providing an alternative route for the reaction.. This increases the number of effective collisions. A collision theory is used to explain how the 6 factors affect the rate of reaction.
Collision theory
- The reacting particle must collide with each other.
- There must be sufficient energy in the collision to overcome the activation energy.
Variables
All the possible variables that speed up the rate of reactions include, the concentration, the pressure, temperature, surface area, light and Catalysts.
I have decided to only monitor the rate of reaction on the amount of concentration used.
Trail experiment results
Prediction
I predict that as the concentration in increased so will the rate of reaction. This is because, as I have said, the more concentration there is the more chances of acid particles colliding with other particles. So the more effective collisions there will be.
I also predict this, as from my trail experiment it shows that as the more amount of Hydrochloric acid, was added to the Sodium Thiosulphate, the less time it took for the reaction to react. The graph shows the trial results from the trail run.
Diagram
Apparatus
1 Beaker, 1 measuring cylinder, 240ml Sodium Thiosulphate, 0.5m, 1m, 1.5m, and 2m of Hydrochloric acid, stopwatch, a piece of paper marked with a cross, and goggles.
Method
- We marked an X on a piece of paper, and placed it under the beaker.
- We then measured 20ml of Sodium Thiosulphate with the measuring cylinder, and added this to the beaker.
- Afterwards we then started adding 2 drops of Hydrochloric acid into the beaker, starting with 0.5m of Hydrochloric acid.
- When all the Hydrochloric acid was added we timed how long it took for the X to disappear.
- We then continued testing it with 8 drops then 10 drops, for all four of the Hydrochloric acids (0.5m, 1m, 1.5m, and 2m). Using s new solution of Sodium Thiosulphate each time.
We only took 3 readings for each Hydrochloric acid, and didn’t repeat any readings.
Safety
For this experiment goggles will have to be worn, to protect the eyes from the chemicals used.
Fair test
To ensure that it will be a fair test, only one variable will be changed this is the concentration added. The rest of the variables will be kept the same this includes, the temperature, pressure, light, surface area, and no catalyst will be used for this experiment.
Results
Conclusion
The graph shows that the more amounts of Hydrochloric acid drops that were added in the Sodium Thiosulphate, the faster the rate of reaction was. In other words the graph shows a decrease of time taken, when more concentrated was added. The more molar that the Hydrochloric acid contained had meant the faster the rate of reaction was.
For example, when using 0.5m of hydrochloric acid with 4 drops it took 5.15 seconds, and when using 2m of Hydrochloric acid with 4 drops, it took 1.15 seconds for the X to disappear.
My prediction was right, that concentration does affect the rate of reaction. This is because increasing the concentration of the reactants increases the number of collisions between particles, and therefore increasing the rate of reaction.
Evaluation
I would say my experiment went quite well, my results are quite accurate as there isn’t any anomalous results shown in the graph. I think my results from the experiment are good enough evidence, to show that the rate of reaction would increase with more concentration. The graph showed this, that the rate of reaction increased with more concentration at a steady rate for each amount of Hydrochloric acid added. I had made sure it was a fair test by only changing one variable, which was the concentration (the amount of Hydrochloric acid).
I could improve this experiment by repeating the readings and working out an average for each one. As I can’t get a very accurate reading for the time it for the X to disappear, with just one reading. By repeating reading and working out averages, I would get a clearer picture of how long it would take for the reaction to happen.
I could also improve measuring the rate of reaction, by doing a different and more accurate experiment. This experiment would be more accurate than the ‘Disappearing X’ experiment. The following reaction can be followed by measuring the gas evolved under a period of time, the diagram below shows how the experiment would be set out.
It shows a reaction between Magnesium and Hydrochloric Acid.
The following reaction would take place:
Magnesium + Hydrochloric acid Magnesium Chloride + Hydrogen
= Mg + 2HCI MgCI2 + H2
The Cornical flask contains Hydrochloric acid with Magnesium ribbon in it. The Hydrochloric acid would contain a particular amount of acid in it (0.5m, 1m, 1.5m, etc). When the Magnesium ribbon is put into the acid the volume of gas would be measured every 15 seconds, until it had stopped reacting. The amount of Hydrochloric acid that would be used would include 0.5m, 1m, 1.5m, and 2m. This experiment is more reliable and more accurate than the ‘Disappearing X’ experiment.
Overall, I do think my evidence is quite reliable as my results show what I thought they would. Also my experiment went quite well, as I had proved what I had set out to do, which was to prove that concentration does affect the rate of concentration.