Rate Of Reaction O example essay topic

The Factors That Affect the Rate of a Reaction Planning: There are different factors which can affect a rate of a reaction such as: o Temperature o Surface area o Concentration o Catalyst Concentration - If the concentration of a solution is increased there are more reactant particles per unit volume. This increases the probability of reactant particles colliding with each other Pressure - If the pressure is increased the particles in the gas are pushed closer. This increases the concentration and thus the rate of reaction. Surface Area - If a solid is powdered then there is a greater surface area available for a reaction, compared to the same mass of un powdered solid. Only particles on the surface of the solid will be able to undergo collisions with the particles in a solution or gas. In this experiment I will be looking significantly at concentration how it can affect Sodium thiosulphate in a solution, the rate of a reaction will increase.

From my previous work I learnt that: In a cold reaction mixture mixture the particles are moving quite SLOWLY - the particles will collide with each other less often, with less energy, and less collision will be successful. Increase in temperature faster speed... More collisions... If we heat the reaction mixture the particles will move more QUICKLY - the particles will collide with each other more often, with greater energy, and many more collisions will be successful. Preliminary work: we conducted a similar experiment to see how long a liquid would take to go opaque when you varied the concentration of acid, water and sodium. I know that this pre-test will help me because now I know the right amounts of solution, water, hydrochloric acid and sodium sulphate.

To make sure the experiment is fair I will perform the following procedures: o o There was a constant volume in all of liquid in all of the experiments. o o Completely rinse all of my apparatus. I will do this so I remove all the particles from previous experiments allowing for the right concentration. o o I will make sure that all the chemicals are measured correctly for accurate results. o o I will not stir the chemicals at all, and try to move them around as little as possible, this is to prevent any unwanted collisions which may speed up the rate of reaction. o o I will make sure that the measuring cylinders are not mixed up for the Hydrochloric Acid and Sodium Thiosulphate. In each of the concentrations done or temperatures the time will be in seconds and will recorded 3 times, this will be done so a mean average can be taken for accuracy in the results. In the group there will be three people watching the solution go cloudy and for the 'x' to disappear and the timer will not be stopped until every one had agreed that the 'x' had disappeared completely.

The flask that the experiment will be done in will be washed out so that the acid and sodium thiosulphate has all gone so the result will not be affected thus making it less accurate. We will take great care when measuring the solution in the meniscus. In this experiment I will be using a stop clock, measuring cylinder, graduated pipettes and test tubes, conical flask, and a piece of paper with an 'x' on it. The apparatuses we have used were 4 beakers, sodium solution, hydrochloric acid, water, 2 measuring cylinders, and a ruler. Safety: Goggles will be worn at all time because strong acid is being used and no running at any time First I will measure the right amount of both Sodium Theo sulphate and hydrochloric acid then I will add Sodium Theo sulphate to conical flask if I need to heat to the right temperature. Then I will put the flask down on the cross then I will add hydrochloric acid and begin to time.

I will measure at least 3 results from room temperature. I will do this twice this also makes my result more accurate... There is also the problem on when to measure the temperature at the start of it, I have decided to plot rough graphs to make sure that the results fit a line then I can repeat those which don't look right. I intend to improve the accuracy of my result by doing each test 3 times to find out the average and then I added it to the nearest second to round it up. There are different methods that I can use to carry this experiment such as light source method using transmitter and light source detector, this method is much easier to use because eye difficulties to see cross disappearing. Light source still can see how much percentage is left even 1% of light is still visible.

Prediction I think that as I increase the concentration of sodium thiosulphate, provided that no other variables affect the results, the rate of reaction will also increase. I believe that this will happen because of the way in which the two chemicals react. When the sodium thiosulphate and hydrochloric acid are placed together in the conical flask, their respective molecules get mixed together, moving freely. When molecules from each chemical collide, they react, forming new compounds.

The concentration will increase the rate of reaction because if the concentration is higher, then there will be more molecules of sodium thiosulphate in a given volume, and so it is reasonable to say that it greatly increases the chances of one of those molecules colliding with the hydrochloric acid molecules. This means That more of the molecules will be colliding and reacting within a given time, and so the rate of the reaction has speeded up this can be justified by relating to the collision theory. Obtaining: While working all safety procedures were followed very carefully like the use of safety goggles and putting the bags under the table. The measurements I feel were fairly accurate as the results were what was expected.

There was some anomalous result, however, which was repeated to get a more accurate result. We repeated the experiment three times so we could find averages and get more accurate results. The results were measured to the nearest centimetres cubed because this was the maximum accuracy of the cylinders. The results show the results we got for each experiment. I did two different graphs showing my results 1 showing the amount of water and the time taken and other showing the concentration and the time taken. All graphs and results are on separate pieces attached to this section!

Analysing: All results have now been obtained and they seem to be quite good, all showing correlation as expected at the start, repetitions were managed for each test and averages were worked out from those figures. From my results I can clearly see that they agree with my prediction, the faster the reaction the higher the concentration My predictions have been accordingly close to reality. When the concentration of the sodium thiosulphate has gone up, as the first part of the experiment shows, the rate of reaction goes up as well. This is what was expected and therefore makes it highly unlikely that there have been any major errors, although all results are obviously not been perfect. In this experiment I have found that as the temperature and concentration is increased the time taken for the reaction to take place decreases. This means that the rate of reaction increases as it takes less time for a reaction to take place, so more particles collide together as a higher surface area is provided per second.

Evaluation: I think that my observations and measurements were very good because I had a lot of pre experiment preparation including the preliminary time I was given so that I could practice my experiment. From this time I had been given to practice, I made sure before the real experiment that I had prepared everything properly so that on the day I wouldn't have to worry about things, if I was doing them correctly, and because of the previous experience I knew what to look out for as well. I think overall my experiment was accurate even though there were probably some human errors but I know that improvements can be made for example at the beginning there were controversies when the room temperature wasn't the appropriate and the water that we used was hot and it obviously would affect the rate of reaction, however, luckily it did not affect much the concentration. Apart from that there were not any other inconvenient. Now at the end of my experiment I can confirm that the point I made at the beginning about the factors that may affect the rate of a reaction is true, the increasing of concentration, surface area, temperature, adding catalysts will positively concern in the rate of a reaction. All the procedures that I used worked fine and I am gratify with the work done, my method endorsed me to get the appropriate precise result needed to sustain my hypothesis.

In order to improve the experiment I would make sure the right amount of hydrochloric acid or probably sodium thiosulphate is measured accurately, this could be some of the reasons why there are some uncharacteristic results in the graph, but I am sure that it can be enhanced.