I will use 5 grams of marble chips and I will use a concentration of 2 Molar.
Results of preliminary work
This shows me that it is better to use new chips every time because it is more accurate and the results are closer together. This happened because when I used the same chips over and over again some of the Chips reacted with the acid, which meant the surface area got smaller which meant the reaction took longer but with new chips each time the surface area stays approximately the same which means the times are approximately the same.
Prediction.
The more concentrated the Hydrochloric acid the quicker the reaction will take place because there are more HCl particles than H20 which means there will be a higher possibility of more collisions between the two reactants HCl and CaCO3, this means the reaction will take place quicker.
I predict that when the concentration is doubled the rate of the reaction will be doubled because when the concentration is doubled the probability of the HCl particles hitting the CaCO3 is also doubled; therefore the reaction will occur twice as quick.
Anticipated Range of results
To find out what concentrations I will use I have to do mole calculations to see if the amount of CO2 given off is sufficient. I want to time how long it takes for 20cm3 of CO2 to be given off so I must check whether the lowest concentration will give off enough CO2 in the initial part of the reaction. I will work this out by doing a simple mole calculation
Vol. of CO2 (in cm3)=moles*24000
0.4*24000= 960cm3
This tells me that there will be sufficient CO2 for the results I will be taking.
The range of results I will take are as follows:
Number of readings you intend to take.
I am going to take three readings for each concentration, and then I will work out an average. I am taking three readings in case an anomaly occurs if an anomaly does occur I will not add that result to my average and make an average out of the other two results.
Method.
- Set up apparatus as shown below.
- Weigh 5 grams of marble chips and put them in the conical flask.
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Make the concentration of HCl and H20, first it will be 50cm3 of HCl and
0cm3 of H20.
- Start the stopwatch.
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Wait until 30 seconds has passed then pour in the solution and time how long it takes for 20cm3 of water to be displaced.
- Take 30 seconds off the time to get the true time.
- Fill in table.
- Repeat the experiment three times using the same concentration.
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After you have done that repeat the experiment using the concentrations: 40cm3 HCl + 10cm3 H20 then 30cm3 HCl + 20cm3 H20 then 20cm3 HCl + 30cm3 H20 then 10cm3 HCl + 40cm3 H20.
The apparatus I need are as follows:
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1 50cm3 measuring cylinders
- 1 Tub
- 1 Stopwatch
- 1 Conical Flask
- 1 Bung
- 1 Top pan balance
- 1 Burette
Accuracy:
To obtain the up most amount of accuracy I will get down to the same level as the burette while measuring the quantities of chemicals used. This will stop any misreads because of the angle I am standing at. I will make sure that my HCl and my H2O does not get contaminated. I will also make sure that I use the same number of chips and of the same relative size also I will make doubly sure that the mass of the chips is right. I will also use a burette, which is very clear to read and is very accurate and lastly I will be using a balance, which measures to a 100th of a gram.
Reliability
I will do 3 tests in case something goes wrong in 1 of them I will be able to take an average of the other 2.
Safety
While obtaining my results I will wear eye protection because I am dealing with acid and if I get an acid in my eyes, they could become damaged.
Results
Analysis
My graph and my table show that as I increase the moles the rate of reaction rises as well.
There are quite a few trends in the graph I have drawn. One of the trends is that the results all go up in a straight line this happens because the reaction never speeds up quicker than normal which would produce a curve. Also as I have said before when I increase the concentration the rate increases as well. It also shows that the rate of reaction between dilute hydrochloric acid and Calcium Carbonate is directly proportional to the concentration of the hydrochloric acid (if the volume of acid and the temperature are kept constant throughout the experiment.)
Conclusion
When I increased the concentration of the Hydrochloric acid the number of molecules of Hydrochloric acid in a given volume increased, which meant there are a higher possibility of collisions between the Hydrochloric acid molecules and the Calcium Carbonate particles, this means the rate increases. With this in mind and using my graph we see that when you double the concentration of Hydrochloric acid, which means that the number of Hydrochloric acid molecules double in a given volume, this means that the chance of collisions between Hydrochloric acid molecules and Calcium Carbonate molecules doubles, which means the rate doubles, for example when the molarity is 0.5 the rate is 1.6 and when the molarity is 1.0 the rate is 3.2 this shows me that my conclusion is right. This gives a straight-line relationship between rate and concentration.
My prediction compared to my Conclusion
My conclusion is more or less the same as my prediction. I came to this prediction by reading many chemistry books on the subject and deducing a prediction from all the information sources I had.
Evaluation
The evidence I collected I believe was quite accurate. I only had one anomaly which was in test 2 of the concentration: HCl: 40 + H20: 10.
This probably occurred because the bung was not secure in the conical flask which may have led to contamination or leakages of gas.
In my opinion there were flaws in the method of testing. There were too many things to do at the same time for example, I had to pour acid into the conical flask and secure the bung and I also had to put the end of the tube under the measuring cylinder. To overcome this flaw I believe it would be best to do the test in a group of at least five so the tasks can be shared. Another flaw was the difficulty of getting a precise reading for the displacement of gas, to combat this next time I will use a stand which would hold the measuring cylinder in place.
The evidence is sufficient to support my conclusion. There was only one anomaly, this occurred because of the reasons above.
Further work I could do to provide additional relevant evidence could be doing more concentrations like 0.5, 1.0, 1.5 molar etc. because it would be interesting to see if the results also follow the trend of my graph. Also I might obtain evidence to see how catalysts, temperature, or surface area affect the rate of reaction.