Rates of reaction.

Chemistry coursework rates of reaction

Background theory

For a reaction to take place the two or how ever many different types of particle have to collide. The faster and more of the particles colliding the faster the reaction will go. To increase the speed of the reaction you can put more energy in to the reaction, the more energy in the reaction the more likely the particles are to overcome the activation energy. The activation energy is the amount of energy needed for the reaction to take place.

There five ways of increasing the speed of a reaction these are;

Increasing the concentration

If the concentration of a solution is increased there are more reactant particles per unit volume. This increase the probability of reactant particles colliding with each other.

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 collision with the particles in a solution or gas. Energy is transferred between the colliding particles…

Increase in temperature

When there is an increase in temperature the particles are given more energy, the now move faster and are far more likely to collide than they would be at a lower temperature.

Use of a catalyst

A catalyst works by providing an alternative reaction pathway that has a lower activation energy.

Increase in pressure

If the pressure is increased the particles in a gas are pushed closer together this increases the concentration and thus the rate of reaction.

Plan

Aim

For this experiment I intend to find out what effect an increase in temperature and concentration has on an experiment.

Equipment

Beaker
Measuring cylinders
Breaker
Tripod
Stopwatch
Goggles

Safety

I will take care when ...

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A catalyst works by providing an alternative reaction pathway that has a lower activation energy.

Increase in pressure

If the pressure is increased the particles in a gas are pushed closer together this increases the concentration and thus the rate of reaction.

Plan

Aim

For this experiment I intend to find out what effect an increase in temperature and concentration has on an experiment.

Equipment

Beaker
Measuring cylinders
Breaker
Tripod
Stopwatch
Goggles

Safety

I will take care when handling the chemicals and were goggles at all times. When handling hot breaker and other hot object a pair of tongs will be used.

Method

I will measure 20mm of each chemical each time, both the solutions concentration will vary depending on how much water I chose to add. I will then mix the solutions in together in a beaker that has been placed over a black cross on a petrie dish, when the cross is no longer visible the reaction is finished. The reason for using 20mm of each solution is when we did our preliminary experiment, is we found that if we had any less than 20mm the cross would stay visible and if we use to much the experiment would be to quick. I will Repeat the results and averages will be taken to improve the credibility of the findings, and present solid grounding for the final conclusion. The repeat results will help to iron out any anomalies and the average will give a good summary of the results of the experiment. However if one set of results is entirely different to the other, a third experiment will be performed to replace the anomalous set of results

Fair test

To make this experiment a fair one I will take the following precautions; I will always look at the cross from the same distance and angle, I will be careful not to mix up any chemicals left in the wrong measuring cylinders and I will wash all the equipment between each result.

Prediction

Using my background theory I have put together a prediction. For the experiment I predict that the stronger the concentration the faster the reaction will be. This is because when the concentration is increased there are more reactant particles per unit volume. This increases the probability of a reactant particles colliding.

Variables and constants

The concentration of the two chemicals will be different
The temperature the reaction takes place will be the same
The amount of light will be the same
The place and angle that the beaker is observed from will be the same
Total volume of liquid will be the same in each experiment

results

Analysis

Conclusion

In conclusion I have done this experiment to an exact degree of precision making sure that my results have a minimal number of anomalies. After studying the results carefully I have to conclude that the stronger the concentration of a chemical the quicker the reaction takes place. I drew a graph and it showed as the concentration decreased as the time taken proportionally increased, as the concentration decreased the time increased more so the graph formed a curve.

The results do support my prediction, and the logic behind my prediction. The reason that the reaction rate increased as the concentration increased was, because there are more reactant particles per unit volume there was a bigger probability of the particles colliding, to fully understand this we have to recap on the collision theory.

In a reaction there are so many particles of each type, in this case sodium thiothusphate and hydrochloric acid, when these particles collide a reaction will occur, but it’s not quite that simple if there a collisions and there is not enough energy, the activation energy is not reached. If the activation energy is not reached the reaction cannot occur, so if there’s more particles colliding there’s more chance of them reaching activation energy and reacting, the more colliding the quicker the reaction can take place.

Evaluation

The results I obtained In this experiment were of a fairly good standard, and my method and recording of results were also satisfactory, but I do think that there could have been be accuracy used. The average results were pretty good, but when looking at set three I have notice an anomaly 0.040 and 0.035 are practically the same and 0.035 should be at lest 5 or 6 seconds long. Fortunately the average has not been completely ruined because of sets one and two.

The method was a good one, but it did include some human error, I would have thought that there would have been a better way of telling when the reaction was finished than looking over it. If I did the experiment again I would have definitely done more sets of results for a better degree of accuracy.

The results were full of human error and can never really be exact unless I find a better method of doing the experiment. Because of this the conclusion can be right, in that it will state that concentration increases speed, but it won’t make a good enough graph to show a great degree of accuracy in the conclusion. I think the anomaly will have been human error that was bound to happen, because of poor judgement.