Pressure: An increase in pressure in a reaction causes an increase in concentration as well because the increase in pressure brings the particles closer together, resulting in more successful collisions.
Method.
1. I will weigh out 6g of marble chips, using the electronic scales because it shows the most accurate readings.
2. I will measure out 50cm3 of 2.0 Molar HCL, using a burette. Then I will pour this into a volumetric flask and measure its temperature, using a thermometer.
3.Then I will add the marble chips to the acid and start the stop watch.
4. Pour the acid into the conical flask.
5. Drop the small marble chips into the conical flask, push in the bung and start the stopwatch as quickly as possible.
6. When the watch has reached 30 secs measure the amount of gas that has been collected in the gas syringe. Record the results.
7. Repeat this three times for each set of concentrations
Safety
- Don’t breath in dust from marble chips.
- Keep liquids away from electronic equipment.
- Safety goggles=acid spray/dust.
- Pour acid into burette at eye level
- Wash off any acid that comes in contact with skin. Spills- mild alkali to neutralize.
Apparatus List.
1. Boiling tube , 50ml.
2.Rubber bung.
3.Small beaker,100ml
4.Weighing boat.
5.Thermometer.
6. Marble chips=small.
7.One-hole bung.
8. Rubber connector
9. Xcm3 of acid.
10.Wash bottle.
11.Spatula
12.Beaker, 250ml
13. Stopwatch.
14.Burrette, 0-50ml.
15. Burrette holder.
16.Boss
17.Clamp.
18.Retort stand.
19.Trough.
20. Thistle.
21. Side-arm flask.
22. Delivery tube.
23. Deionised water.
24.Volumetric flask.
25. Electronic scales.
Fair test
Controlled variables.
-
Size of chips.
- Volume of water in trough.
- Size of boiling tube.
- Volume of HCl.
Dependent-Measure
Independent Variables.
Reliability.
To keep the investigation a fair test there are certain factors which need to remain the same.
- The marble chips mass be kept constant because marble chips of different masses would mean the reaction may take place more quickly or slowly.
- The volume of Hydrochloric acid must remain the same because this would also effect how fast or slow the reaction took place depending on how much of the marble chip was covered by the Hydrochloric acid.
- The temperature of the Hydrochloric acid must also be kept at a constant temperature due to how quickly or slowly a reaction takes place
Accuracy
To ensure my experiment is as accurate as possible I will measure the solutions very accurately. I will do the same when measuring the marble chips, the weighing scales I will be using are correct to 2 decimal places. I think 2 decimal places are accurate enough for this experiment as I am only using the weighing scales to measure the marble chips.
I will repeat the experiment three times to make sure my average consists of a good range of results. The hydrochloric acid goes up by 0.5 molar every time so our results will not be too similar. A good range of results will be produced. If I find any anonymous results I will record them but then I will repeat the same test to see if I get a result which follows some sort of pattern.
I will record my results accurately to 2 significant figures.
Prediction
Using my scientific knowledge I predict that as the concentration of the acid increases the rate of the reaction will accelerate causing Carbon Dioxide to be given off at a faster rate. I know this because there are more hydrochloric acid particles in the higher concentrated acid to collide with the particles in the marble chips. I came to this prediction because the more concentrated the acid the quicker it will break down the Calcium Carbonate to form Carbon Dioxide, water and Calcium Chloride. The equation shows this:
2HCL + CaCO CaCl + H O + CO.
TIME TO REACT.
There is a minimum amount of energy which colliding particles need in order to react with each other. If the colliding particles have less than this minimum energy, then they just bounce off each other and no reaction occurs. This minimum energy is called the activation energy. The faster the particles are going, the more energy they have. Fast moving particles are more likely to react when they collide. You can make particles move more quickly by heating them up (raising the temperature). Increasing the concentration of a substance in solution means that there will be more particles per dm3 of that substance. The more particles that there are, the more will collide per second, and so the rate of the reaction increases. In the reaction between marble chips and dilute hydrochloric acid,
Interpreting and Evaluation.
Result Graphs
As the concentration increases, time for the reaction to finish decreases.
As the concentration increases, rate of reaction increases. The Rate is directly proportional.
The results support my conclusion. My results are in a straight line and there is a line of best fit showing that it is directly proportional. When you use higher concentrations between CaCO3 and acid ions, the rate of reaction increases. This means that there are more ions colliding because there are more ions to collide with as the concentration increases.
I think this was a suitable experiment to find the rate of reaction between HCl and marble chips. I got some good results and the tests were repeated for accuracy inc ase of any anomalies.
Evaluation: Overall my investigation was good, because it was safe and produced fairly accurate and reliable results. The anomalous results I have pointed are mostly due to the chip size. But other factors may have affected my results. The temperature in the room may have risen while we were in there making the reaction speed up. To make sure the temperature would be the same for all experiments I would have to monitor the temp. of the room often and if necessary would put the conical flask into a beaker of water that I would control the temp. of. I also may have measured the wrong amount of water or acid. To resolve this I could use a larger measuring tube that, I would then be able to see the measurements more clearly. To make the test a fairer, I could try and make the size of the chips the same, although this is almost impossible, since all marble chips are different. To make my results more accurate and reliable I could repeat the experiment a total of five times or more. The reaction could have speeded up due to human error because the conical flask could not have been washed out properly. So some acid could have been left in the beaker, making the reaction speed up. Then making my results wrong. I could try the reactions at different temperatures. I could then find the optimum temperature for the reactions to take place at. I could also try different acids such as sulphuric acid and nitric acid; I could then compare the results and ascertain which acid reacts more quickly with the marble chips.
Conclusion.
I have been able to successfully test the relationship between the rate of reaction between HCl and marble chips, depending on their concentration. The rate of reaction is directly proportional to the concentration, this agrees to the prediction I made. Increasing the concentration,, also meant the increase of H ions in the solution, which means that there will be more collisions between the particles. To me my results were accurate enough and the predictions I made were conclusive
