Preliminary testing:
In this test my aim was to try and find out whether the range of concentrations between 0.5 and 2 Moles/litre was a suitable one given the amount of time I have.
Apparatus:
-Conical flask with bung with a delivery tube
-Clamp stand
-Gas syringe
-Measuring cylinder x2
-Timer
-Marker pen
-Scales
Method:
-I mixed up acid solutions in two concentrations, 2 Moles/litre and 0.5 Moles/litre, using the method shown below.
-I then took an acid, in a conical flask, and added the marble chips to it
-I placed the bung in place at the same time.
-I started the timer simultaneously
-I then drew a line using the marker pen showing where the plunger in the syringe was up to at 5 and 10 intervals, for the 2 and 0.5 Moles/litre acid mixtures respectively.
-I then recorded the readings clearly in the tables.
Results:
2 Moles/litre concentration:
0.5 Moles/litre concentration:
Analysis:
These two tables show me that the range is acceptable as neither concentration react very slowly. However, I can tell that it would be better to measure the 2 Moles/litre acid’s reaction every 3 seconds as opposed to every 5 so that I can get enough readings to plot a suitable graph. Measuring the 0.5 Moles/litre acid every 10 seconds is fine as it reacts at a slower rate.
Method plan:
Apparatus:
-Conical flask with bung with a delivery tube
-Clamp stand
-Gas syringe
-Measuring cylinder x2
-Timer
-Marker pen
-Scales
Set up as below:
Substances:
-Water
-Hydrochloric acid in 2 Moles/litre
-Medium-sized Marble chips (calcium carbonate)
Plan:
-I will start by measuring out the marble chips into 10 x 7-gram quantities
-Then I will make up acid and water solutions of 50 cm-cubed in different strengths:
-I will get a solution of 0.5 Moles/litre by mixing 12.5 cm-cubed acid with 37.5 cm-cubed water.
- I will get a solution of 0.75 Moles/litre by mixing 18.75 cm-cubed acids with 31.25 cm-cubed water.
-I will get a solution of 1 Moles/litre by mixing 25 cm-cubed acids with 25 cm-cubed water.
- I will get a solution of 1.75 Moles/litre by mixing 43.75 cm-cubed acid with 6.25 cm-cubed water.
- I will get a solution of 2 Moles/litre by using 50cm-cubed of acid straight from the beaker.
-I will repeat the previous five stages once more so that I can repeat my tests twice.
-I will then take an acid, in a conical flask, and add the marble chips to it
-I will place the bung in place at the same time.
-I will start the timer simultaneously
-I will then draw a line using the marker pen showing where the plunger in the syringe is up to at certain intervals, depending on the strength of the acid.
-I will then record the readings clearly in a table
-I will repeat this for every acid mixture I have made.
Safety precautions:
-I will wear goggles to protect my eyes
-I will wear a lab coat to protect my clothes and body.
-I will not use acids that will severely harm anything.
Fair test:
-I will aim to get the marble chips the same size so that the surface area will be the same and not interfere with my results.
-I will use the same amount of solution for each test so that it won’t affect my results.
-I will perform all of my tests at room temperature so that it won’t alter my results.
-I will use the same weight of calcium carbonate.
Prediction:
I predict that as the concentration increases, so will the rate of reaction. I think that this will happen because when a solution is more concentrated, there are more particles of the acid in it, which means that there will be more particles to collide with the calcium carbonate molecules. This is clarified in the diagrams below:
Obtaining Evidence Section:
The results from my investigation are below:
0.5 Moles/litre concentration:
0.75 Moles/litre Concentration
- Moles/litre Concentration
1.75 Moles/litre Concentration:
2.0 Moles/litre Concentration:
Analysing Evidence Section:
I have calculated the initial rate of reactions for all of my tests:
Conclusion:
I conclude that as the acid solution grew stronger, the rate of reaction increased. This means that my prediction was correct. I believe that this is because there are more particles of acid in a concentrated solution, so there are more particles for the solid to collide with. Therefore there are more successful collisions, and the rate increases.
How well do my results support my prediction?
My results support my prediction very well as they show my theory exactly. The rate has increased by 2.67 s .
Evaluating Evidence Section
The suitability of my method:
I would strongly recommend my method to anyone else wishing to investigate the effects of concentration on the rate of reaction. My method was very simple and, given the limitations of time and equipment available, produced fairly good results.
Improvements to the method:
I would repeat the tests at least five times so that they are more accurate. When the are repeated more, the margin for error is narrower and I cane get a better set of results.
I would use a shelf in my conical flask. This would allow me to put the marble chips into the acid but be ready to measure the carbon dioxide instantly.
The accuracy of my results:
My results seem altogether quite accurate. There were no anomalous results, however a few points strayed a little from the line of best fit.
I think that the reason a few of my results were a little out, is that all the tests were conducted in an environment in which the temperature was unmonitored. The tests were performed at room temperature on two separate days. This means that my test conditions may well have been hotter on one day than the other or there may have been a draft, and as temperature is a variable in this investigation, it might have affected my results.
Another reason may have been due to the delay in between my putting the marble chips into the acid and fixing the bung in place. This delay will have allowed some carbon dioxide to escape, but as this delay was roughly the same in each test and we are looking at rate rather than actual volumes of carbon dioxide, I doubt it affected my results significantly.
Extending this investigation:
To test my prediction further I can do a number of things:
- I can test many more concentrations.
- I can test it using a different acid.
- I can use a different solid.
- I can test it with different amounts of solid.
