Rates of reaction.

Investigating the effect of concentration.

In this test I am going to use different concentrations of acid: 0.25, 0.5, 1.0, 1,5 and 2.0. I am using a different concentration of acid to find out a number of answers so I can see if the concentration affects the speed of the reaction.

Predication

In this experiment I predict that as the concentration gets higher the time will be higher each time. The concentration of acid will affect it because it will have a higher amount of particles in each time so this causes more collisions within the reaction. I will need to collect reliable information and data to make this a supportable predication.

I have predicted that through the knowledge from what I have gained from my research. I have found that if I wanted to predict my rates of reaction, the collision theory will be useful to know about. This is because the collision theory is used to predict the rates of chemical reactions. This is because the collision theory is used to predict the rates of reactions. The collision theory is based on the assumption that for a reaction to occur, it is necessary for the reacting species to come together or collide with one an other. Not all collisions however bring out a chemical change.

HYPOTHESES

A reaction occurs when particles collide. This process is based on random particle movement. So therefore, the more particles you have in a space, the more likely they are to collide. Therefore it makes the reaction accelerate. This theory can be proved if you compare the rates of reaction with marble in hydrochloric acid. 'If the acid is of a higher concentration, the reaction will be quicker. Also if the particles have more energy, they will be travelling faster, making them collide more frequently.

Equipment

• Gas syringe
• Conical flask
• Delivery Tube
• Clamp
• Clamp Stand
• Rubber bong
• Stop watch
• Measuring cylinder

Method

First of all I would do a table that records the time and how much gas there is in the gas syringe. Then I get the certain equipment listed and then I would arrange them in the order of the diagram. Then I put 2gs of marble chips into a conical flask. Then I would add 30ml of concentrated acid that I measured with a measuring cylinder. I then would put the rubber bong on the flask with a delivery tube through the rubber bong. From here and on wards I would record how much gas is coming out with a gas syringe. Then I would repeat this to all the other concentrated acids(5). Since I will be working with strong acid, I will wear safety goggles while conducting the experiment. I will use Marble chips all of a small size. I can use a sieve and scales to make sure they are all roughly similar size, about 7mm diameter. If the experiment goes on for a ridiculous time, I will cut it off. I don't think it is necessary to have the experiment go over three minutes, so I will cut it off then. Also, if the amount of gas goes off the scale I will stop it there.

Preliminary work

I have carried out an experiment for investigation in safety, accuracy and reliability.

This is the results from my preliminary experiment this helps me because now I know what to do in the near future and what I should set my lowest and highest time. It also helps me by it showing me what precautions to set. Like to have the equipment all the same all the time so it is a fair experiment. From this I can now make the time shorter to fit all the volume of CO2 results.

I can see from my preliminary work that it is quite hard to start a stopwatch, pour acid and stick a bung into a boiling tube all at the same time, so I will get someone to assist me while doing so.

Investigation results

I have carried out the real investigation now and I have used the same method as my preliminary work. I will try to keep this is a fair test and try to realise the rates of reaction. I am going to do three experiments.

Fair Test

In this test I am going to make it fair by making sure all the equipment is the same and that the only variable is the concentration of the acid. I will need to keep the calcium carbonate at the same weight each time to keep the test fair. Also make sure that the acid has the same amount each time or the test will be biased.

Results

Here are my results for the three experiments I have done.

From these results I can see that they all fit into a pattern.

I am now going to put these results into averages and eventually graph them to see what the rates of this reaction are with different types of concentrations.

I have tabled my results and I have put them to the nearest decimal. I have also worked out the averages and this shows me that the averages get higher the concentration which proves my hypotheses. I am now going to get my averages results and graph them.

These graphs show the average volume of gases. These graphs also show my hypothesis to be true and that the volumes of gas do go up in each concentration. I can see there is a pattern of volumes and this is that the higher the concentration the higher the volume of gas.

Evaluation of Experiment

I believe that I do have an accurate set of results and that I do have enough results to be sure about my conclusion. However, I feel that I could have gained even more accurate results and therefore an even more accurate conclusion, if I had taken more readings.

Looking at my graphs there do not appear to be any anomalous results because they all follow the trend well and fit into the pattern. However I feel that as I lowered the concentration and the time increased the results became more varied. This can be shown in the way that there was a percentage difference in my two results bigger than 10%. Although I feel that this could have been caused by human error when deciding when the way I was looking at the marks on the side of the gas syringe. My method of carrying out my experiment was fairly accurate. I made sure that I washed the beakers clean for each reaction I had and I measured the same amount of solution in each time. Although I think there is a human error factor involved when you are measuring gasess and also looking for an end point in the reaction. ctd5c6qQ

Conclusion

My prediction stated that there will be a positive correlation between the rate of the reaction and the temperature so that as the temperature is increased, the rate of reaction will increase. My results proved this prediction correct as, for example, after 10 seconds the amount of gas given off was:

At each 2 or 1 cm increase, the rate of reaction increased as more gas was given off at each increase of temperature. This is because the reaction needs energy so that original bonds are broken and new bonds can be formed. If the collision has enough energy then the reaction takes place. The more successful collisions there are, the faster the reaction. The more the particles are heated, the faster they move, the more chance there is of particles colliding and the reaction taking place. Therefore, at 2.0 the particles are moving faster and there is more chance of them colliding and when they do collide they are moving faster so the more chance there is of the reaction taking place. It is not only necessary for particles to collide, but also that the collisions have enough energy. Heat provides extra energy, causing particles to both move faster and collide more successfully.

I expected my second graph to show a levelling off at each temperature over a period of time as more atoms and particles were used up during successful collisions. However, this change in rate of reaction as the reaction proceeded was not apparent and my graphs showed straight lines for each temperature when I plotted my lines of best fit. This is likely to be because of the relatively small amount () of CO2 collected (see evaluation) which did not allow each reactant to be used up and all possible collisions completed.

Evaluating evidence

I think the results I collected are sufficient to support a firm conclusion but the reliability of a small amount of the data was in doubt. At 2.0 of concentration and at 100 seconds, Experiments 1-3 had to be ignored in the final averages as an anomalous result. This could be due to experimental error. It may have been that the temperature was slightly higher than 100 cm2 giving a faster result. It may have been that because the results were cumulative, the stopwatch was started too soon for each results being inaccurate.

To improve the accuracy of the experiment, instead of leaving the acid for 10 seconds, I would measure the temperature of the acid and start the experiment when it gets to the correct temperature. This will make the experiment more accurate as I will know the acid has changed to the correct temperature.0 I could also have used a more accurate measure of marble chip by weighing each one.

If more time had been available, I would have allowed each reaction to be completed i.e. waited until all of the carbon dioxide had been given off, so that I could see if the reaction rate for each temperature got slower over time. In order to do this, I would need to change the apparatus i.e. use a larger syringe to collect the gas as the size of the original syringe (100cm2) was a limiting factor