Equipment list
- Large measuring cylinder ( 500ml)
- Water bath
- Delivery tube
- Hydrochloric acid ( 0.4M – 2M)
- Small measuring cylinder (50ml)
- Beaker
- Thistle tube
- Bung
- Marble pebbles
- Petri dish
- Scales
- Spatula
- Stop clock
Method
Preliminary
Before we started on our first concentration of acid, we did a preliminary test to check that all equipment was working and to see the different effects of certain factors, for example we found using smaller marble chips reacted quicker than larger ones as the acid had more surface area to react with. We also did this test to see who was best at inverting the large measuring cylinder without losing too much water, by doing this we saved a lot of time and sorted the minor jobs out between the three of us.
First we set up all the equipment into the right place ready for the first test. As I was diluting the acid into the specific concentration I first had to make enough 0.4M acid for three runs so by following the table I made 100ml of 0.4M hydrochloric acid. While I was doing this, one of my team members assorted the small marble chips into Petri dishes which had exactly 2 grams in them.
These are the tables for the acid solutions:
After we had measured out 25ml of the concentrated acid into the small measuring cylinder and got the 2 grams of marble chips, we were finally ready to start. We put the delivery tube’s end underneath the inverted cylinder so that the CO2 could not escape.
I first inserted the 2 grams of marble chips into the bottom of the flask, then carefully and slowly poured the 25ml of acid into the thistle tube, making sure it did not splash or deflect onto one of us.
From the time I poured in the acid another person started the stop clock and every 10 seconds we drew a line on the measuring cylinder showing the amount of collected carbon dioxide. We did this for 70 seconds and then finally read the results and jotted them down onto a table. After each run we emptied and refilled the water bath, large measuring cylinder, and also emptied the flask making sure we didn’t contaminate the next test. We repeated this whole process of getting the marble chips and acid, emptying and cleaning the equipment 3 times for every concentration of acid until we got a total of 18 successful results.
We made this test as fair as possible by using the same amount of acid and marble chips each test, using roughly the same amount of water in the bath and cylinder, running it for the same amount of time and finally by cleaning the whole set of equipment every time.
In addition we also made sure we kept our safety at high priority over everything and by doing this we made sure we wore safety glasses, slowly moving around when we had acid in our hands and just concentrating on everything we done.
Background information
Concentration is one aspect of the collision theory. The theory is that the higher the concentration of the reactants, the closer the particles are together and this means they will collide more often and this will speed up the rate of reaction. During this experiment we will discover whether this theory is correct.
Activation energy is the amount of energy that must be overcome in order for a chemical reaction to take place, for it to activate. It can also be explained as the minimum energy necessary for a specific chemical reaction to occur. The level of energy needed to activate the reaction can be lowered by using a catalyst. This modifies the transition state which lowers the activation energy. It is important to note that a catalyst increases the rate of reaction without being consumed by it. In addition, while the catalyst lowers the activation energy, it does not change the energy of the original reactants or products. The reactant energy and the product energy remain the same and only the activation energy is altered.
Results
Rate Graph
We did this by drawing a straight line across from 30 on the Y- axis (we did this as it crossed 5 out of the 6 curves) we then jotted down the time it took where the 2 lines crossed. We then done the equation
1/time taken to create 30cm of gas. We then plotted the results onto a graph.
Analysis
I believe the whole experiment was quite safe but there were problems with the higher concentrating acids burning our hands slightly if spilt and staining our clothes if it went on them, to improve this I think we should have worn simple gloves just to keep the safety a bit higher. We also could have concentrated more and moved books and bags out of the way so any spillages did not affect them. We had a few limits on our method because we only had a certain amount of time so we could not make the method very accurate, also because of the amount of people and how much water we were using, it took us a while to start the next run as we had to wait for the water and acid.
We could of improved the whole experiment by preparing all the equipment at the beginning and not getting it when needing it as we wasted a lot of time doing that. In addition after the first few runs we started marking the allocated point every 10 seconds with a marker pen as we found this was easier to collect the results instead of trying to figure out the amount upside down. One of the most important improvements we should have done is defiantly use glove because there was one case where the acid splashed when being poured into the thistle tube which in effect hurt one of my team mates which was lack of concentration but also preparations for accidents.
Evaluation
At the beginning we did have trouble collecting correct results causing us to re start but we learnt from these mistakes and I believe our results in the end were accurate as the range bars were not too big for the lower Acid concentrations but when the acid concentration and time increased the range bars started to also increase in size, even though the last few range bars started getting bigger I think our results still were reliable as each point was generally central of the range bar which shows we didn’t have a massive variety. Luckily we did not get any outliers apart from the unsuccessful results at the beginning of our experiment.
In addition I had confidence in our results because the equipment we used we kept it clean and made it very fair for each experiment by using the same instruments for every test, also none of it broke or had faults which would have given us unreliable results and would of disrupted our whole experiment.
So to conclude that our results were reliable I can say that they are because of a few main factors which are that the equipment worked perfectly and did not have any faults, we made sure the whole test was fair from many ways (collected all the results in one day, changed the water each time, same amount of time on each) the other main factor was that the range bars were not too big which helps secure the confidence in our results.
Conclusion
To finally conclude this, from the background knowledge of collision theory and from my reliable set of result we got, I can say that the more concentrated the acid is, the faster and larger the reaction will be.
