Method of Experiment:
- Before I began the experiment I would source all the equipment (above) this would stop me from rushing around later. I would draw my evidence table (below). Once I had everything I could actually began setting up and completing the experiment.
- Assuming all the equipment is preseant, I would measure the acid (20/30ml) then pour into a chonical flask.
- I would then put the marble chip inside the flask and quickly put the bung on. The bung connects the delivery tube and gas syringe and ensures no gas would be lost.
- Record results at ten second intervals and put the information into my results table.
- Repeat steps with a different molar acid (either 0.1, 0.5, 1, 1.5 and 2)
- Repeat the experiment five times.
To ensure the test is as fair as possible I would have to keep the variables the same. To keep the information as concise as possible I am going to display it below in a table form. In the table I will explain what must be kept constant, and why it must.
Temperature:
For a reaction to happen particles need to collide with enough energy to cause a reaction, increasing the temperature gives the particles more energy making the collisions harder and more frequent therefore more likely to cause a reaction.
Concentration:
Increasing the concentration means there are more particles in the same space increasing the chance of a collision and therefore a reaction.
Surface Area:
Increasing the surface area means there are more particles exposed to the outside so there is a larger chance of a collision and therefore a reaction.
Catalyst:
Adding a catalyst to the reaction increases the temperature by lowering the activation energy of the reaction so it is easier for the reaction to get started.
Prediction:
To chemicals reaction that will occur is below:
2HCL + CaCO H O + CaCl + CO
3 2 2 2
I know that an acid + alkali = neutralisation, when we neutralise something it tends to fizz and give of bubbles. The hydrochloric acid and the marble chip will collide and I think bubbles of CO2 will be given off. This makes sense as this is what usually happens in neutralisation. Also if I were to double the acid concentration I think that they rate of reaction would double. This is sensible as I would expect double the strength equals double the speed. Also the points on my graphs would get steeper the faster the reaction. I think my graphs will in general show positive correlation. This would support my other prediction of the lines getting steeper the stronger the acid.
In summary:
- As we are neutralising something I think it will bubble and fizz. These characteristics are constant for most neutralisation experiments.
- As we are mixing HCL and CaCo3 I think CO2 will be given off.
- If I double the acid concentration I think the speed would also double.
- My graphs will show positive correlation as the lines get steeper.
Safety:
Safety is of paramount importance at all times. To ensure that no health or safety breaches occur whilst I am doing my experiment, I will make sure googles are always wore at all times, not to run in that lab, place stools under the benches and always remain cautious. It would also be helpful to wear latex gloves when handling corrosive substances, as it would provide further protection. A recent study shown that most accidents in the lab occur whilst packing up. Also at this time people remove their goggles to pack up. This is especially dangerous as substances can get tipped into a sink and shoot back up into the face. To minimise the chance of injury I will ensure I wear googles from the begginning of the session until all the equiptment has been put away.
Preliminary Work:
Before I completed all my results, I couldn’t get accsess to a gas syringe. I had to use a measuring cylinder and a plastic container to measure results. I found this was harder to measure and record, so I decided I would only use a gas syringe.
Obtaining Evidence:
To record my results as accurately as possible I designed the below table. I think it is handy as you can clearly record results and easily interpret the data on a graph.
Experiment one: Experiment two:
Experiment three: Experiment four:
Experiment five:
Graphs
All of my graphs show positive correlation which is what I predicted. The all show this trend which is interesting, it proves that the more concentrated the acid the faster the rate of reaction. This is shown by a steep line, which is apparent on all of my graphs.
Although it would be to messy and small to do it is possible to find out how much gas is being produced at a certain time. To do this we must follown the below method:
- Draw a tangent to the curve at an appropiate mark.
- Draw a right angled triangle from your tangent at a convenient place.
- Calculate the slope by working out the tangent of the angle.
Usually the equation would look something like this:
Tangent of x = Opposite (divide) Adjacent = ??.??CM3/S
So it is possible to find how much gas was being produced at a certain time.
If it were possible to calculate the rate of reaction on my graphs, I would draw a large table displaying the results at constant times throughout each experiment. This would give me more evidence to agree or disagree with my predictions.
To make it clear if my predictions are correct I am going to preasent my predictions an actual results in a table and decide wheter they are correct or not.
Evaluating:
I think that overall the experiment went very well. We completed it in good time, had a decent set of results and had no accidents. I am surprised it went so well, we got five results instead of the usual three. We accomplished this by really making use of little time at the end of each lesson, and the beginning of the next. We worked hard to get as many results as we did, and I think our work reflects the effort we pushed in to it.
During the recording of results I expected to find some anomalies present. This however wasn’t the case, as our graphs do not show anything which looks out of place or wrong. I was expecting some anomalies which could occur from human error of recording results, dirty equipment, the wrong strength acid, there is a wide range of possibilities that could have gone wrong.
Improvements:
I think the method we followed was in depth and correct. We followed the method that was given to us, so maybe that’s why we got no anomalies. I think if we had more time to prepare I would make sure all the marble chip was of the exact weight, and the same size. We had to roughly measure their weight on innacurate scales, it was difficult as it was only sensitive to one gram.
Further work:
Once again, if I had more time to complete the exercise I would collect more results. This would provide more evidence and either strenghten my predictions or go against them. As my predictions were all met with five results, I don’t think doing it again would prove them wrong. But if I make more sensible predictions I could do it again and see whether they are correct, or if incorrect, why?
Also to complete it more accurately I could use a wider variety of acids. This way I could complete the exercise with more acids, giving me more varied results, better conclusions and accurate results.