In my experiment Hydrochloric Acid (liquid)(HCl) is going to react with Marble Chips (solid)(CaCO3) to make Calcium Chloride (liquid)(CaCl2), Water (liquid)(H2O) and Carbondioxide (gas)(CO2):
CaCO3 + 2HCl CaCl2 + H2O + CO2
In this reaction energy is taken in, in order to break the bonds between the atoms. More energy is taken in then given out so the reaction is endothermic.
Procedure
Apparatus
Here is a list of apparatus I will use:
- A Burette
- A Measuring Cylinder
- A Beaker or Tub
- A Boiling Tube
- 10ml of Acid
- Water
- 1 gram of small Marble Chips
- A Delivery Tube + Rubber Bung
- Some precise Weighing Scales
- Clamp
- Pipette
Method
To do the experiment I am going to do the following:
-
Fill the tub/beaker full of water, measure 10ml of Acid into the measuring cylinder using a pipette to be more precise, measure 1 gram of small marble chips and put them into the boiling tube (To keep the experiment a fair test I am going to keep this the same when I change my variable), fill the burette with water, put the end of the burette into the tub/beaker upside down holding the end so water wont fall out, attach the end of the delivery tube onto the end of the burette under the water.
- Pour the acid into the boiling tube and attach the bung immediately afterwards so the gas released from the reaction goes through the delivery tube into the burette, read the amount of gas released from the reaction on the burette by looking at the water level and record every 30 seconds for 2 minutes and 30 seconds.
- Repeat this again four more times each time reducing the amount of acid by 2ml and make up the amount to 10ml by adding water, wash all the equipment between each time to make sure experiment is a fair test.
- Repeat the whole experiment again in order to get a mean average for each result and eventually draw a graph.
Results
This is the results table I have planed to put my results in:
Safety
To make the investigation safe I am going to do the following:
- I will wipe up any spillage’s from the bench to avoid burning myself or other people with acid.
- I will wipe up spillage’s from the floor to avoid myself or other people slipping.
- I will keep my apparatus away from the routes of other people so nobody trips over it.
- I will empty the contents of my boiling tube through a sieve into the sink so the marble chips don’t clog up the drain.
- I will immediately clean up any breakages I may make so nobody gets cut by broken glass.
Preliminary Work
From my preliminary work I have learned how much acid and marble to use in order to make my experiment run long enough to plot 5 points, I found 10ml of acid and 1 gram of small marble chips would be enough to slow the experiment down to 2 minutes 30 seconds so I could record the measurement on the burette every 30 seconds. I have also learned how to use a burette and record to 0.1 of a cc.
Results
Here are two tables of results I recorded in my experiment from my first try of the experiment and when I repeated it, they show how much gas was released from the experiment. I have changed the table since I made my plan and it now shows how much water I used with the acid to make it up to ten milliliters.
Try 1
Try 2
This extra table is a mean average table of the other two sets of results, I am going to draw my graphs from these results. All the averages have been rounded up to 1 decimal place.
Average Table
Conclusion
From my graphs I can see that what I predicted was true and that the rate of reaction would speed up with a higher concentration of acid and slow down with a lower concentration of acid.
The pattern of results show me that the gradient of my line of best fit gradually slows down, it also makes me able to predict that if I were to go on taking results I would be able to see the gradient becoming shallower and eventually becoming flat and continuing on in a straight line. Looking at the pattern of results on my graphs for the lower concentrations of acid I can see the line of best fit isn’t so steep and was slower than the other reactions were.
The anomalous points on my graph mean I have done something wrong or something has gone wrong by accident, this may mean I have used to much acid or to much marble chips.
By changing my variable five times I was able to get more results and predict what would happen if I had carried on. This wide range of results helped me to draw a more accurate conclusion because I was able to represent them in the form of a graph and see easily what was happening.
The line of best fit gradually getting less steep and eventually flattening means that the particles in the reaction are making lots of successful collisions and are being used up so the reaction slows down. The shallower gradient and slower reactions for the reactions with a lower concentration of acid mean that as I explained in my prediction, when the concentration of acid is less there are less particles to react so there are less successful collisions and the reaction takes much longer.
High Concentration Low Concentration
Evaluation
My procedure seemed to work and was able to get me the results I needed. It worked well so I was able to make clear recordings of results, unfortunately unknown to me accidents must have happened and I may have used slightly more acid or marble than was needed to keep my results clean and my graphs free of anomalous points.
To get better results I could have used more up to date and more accurate technology. I believe the scales I used were accurate enough as they were so mistakes must have been made on my behalf there, but maybe something more accurate than a measuring cylinder and an easier way of reading from a burette on exactly the right times would be helpful.
By changing my variable a number of times I got a wider range of results which enabled me to draw a more accurate conclusion. I did the whole experiment twice in order to be able to:
- Calculate an average of the two tables
- Have enough information to make a graph
c) Exclude any wild differences in the two sets of results i.e. I may have accidentally taken my pulse wrongly in the first set of results, however, when calculating the average this result was evened out, avoiding an anomalous readings
I think my graphs were good enough to support my conclusion, it shows a clear line of ‘best fit’ that backs up the fact that the higher the concentration the faster the rate of reaction. Through my scientific knowledge I can explain that because successful collisions are happening and particles are being used up the reaction would slowly or rapidly, depending on the concentration of acid, come to a stop. On a graph this would look like the line of best fit would become less steep until becoming flat and continue in a straight line. Another method I could have used to get a good set of results and a clear and clean graph could have been to do the experiment for longer until it stopped or I could do the experiment three or more times instead of two, so when I made an average table it would even out the results even more so I wouldn’t get any anomalous results on my graphs.
Most of my measurements fit on my graphs and a line of best fit can be drawn without any anomalous points being noticeable, but on a few graphs you can see the anomalous points and can make out they do not fit in with the rest of the results on the graph.
On my results tables you an see that on some occasions the results do not make a pattern, for instance the bottom line of my first results table is considerably different to the other points on the table:
If I were to do the experiment a second time I would definitely repeat the experiment at least double the amount of times I repeated this experiment so I could get a better graph and be able to evaluate the results better.
I conclude that making the concentration of acid higher speeds up the rate of reaction and making it lower slows the rate down. What I predicted in my prediction turned out to be right and seemed to be right at least for most of the results I gained.