Fossil fuels give off a small amount of Sulphur, S.
Acid rain will also be a mix of sulphurous and sulphuric acid and a small amount of nitric acid. The statue is reacting with sulphuric and sulphurous acid. The sulphur is coming from fossil fuels.
Equation of acid rain:
S+02 S02
S02+H20 H2S03
My Prediction:
I predict that in summer, it will corrode more because the temperature is higher. When the temperature is higher more reactions will occur because of the increase in collisions.
I also predict that in the winter the concentration of acid rain will be higher because people will burn more fossil fuels in the winter. The increased concentration will increase the number of collisions, therefore more reactions.
Factors that affect the rate of reaction:
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Concentration- Low concentration: particles far apart, few collisions, low rate of reaction. High concentration: particles more crowed more collisions high rate of reaction
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Temperature -Low temperature- few collisions, low rate of reaction. High temperature- more collisions, high rate of reaction.
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Surface area- -Increase in surface area, increases the rate of reaction. Small particles have a larger surface area than a large molecule.
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Catalyst- A catalyst will lower the activation energy and speed up a reaction.
What I will change in my experiment:
I will change the concentration by changing the volume of acid and water but keeping the overall volume the same. I will assume that the acid rain is made up off sulphuric acid. I will use stock 2.2 molar sulphuric acid. I will change the acid concentration only.
How I will control the different factors:
- Temperature- I will keep the temperature the same by conducting the experiment at room temperature.
- Surface area- I will control the surface area by making the magnesium strips the same size and length.
- Catalyst- I will control the catalyst by not using one.
- Light- I will conduct the experiment in daylight.
I will make 5 measurements in the range of concentration, 0.4 molar to 2.0 molar sulphuric acid.
I will also record my results in the form of a table. I will then plot 2 graphs, one of time versus concentration and one of rate versus concentration.
I predict my graphs will look like this:
I will record my results on a table like this:
Apparatus used:
- Beaker
- Measuring cylinder
- Magnesium strip
- Sulphuric acid
- Apron
- Goggles
- Water
- Timer
Diagrams:
My plan:
First, I will measure out a 5cm strip of magnesium. Next I will measure out 50 cm³ of sulphuric acid, using a measuring cylinder, and pour the sulphuric acid into a beaker. Next I will take a 5cm magnesium strip, making sure the strip it is flat, and drop it in the all acid solution. As soon I drop the strip into the acid I will start the timer. I will then stop the timer when the magnesium has completely dissolved and record the time in my table.
I will repeat this 4 more times but I dilute the acid with more water every time. The second time there will be 40cm³ of acid and 10cm³ of water, the third time there will be 30cm³ of acid and 20cm³ of water, recording my results each time. I will continue this until there is 40cm³ of water and 10cm³ of acid in the beaker. I will insert my results into a table, and make graphs of my data.
I will conduct the experiment a second time to get the most accurate results I can
Safety Precautions:
- I will wear an apron at all times.
- I will wear goggles at all times.
- Any acid spills that might happen, I will clean it up with a damp cloth.
- Chairs and school bags will be tucked in under the table.
Possible sources of error:
- Magnesium strip not being placed flat on the surface of the acid.
- Volumes incorrect.
- Time not started correctly.
Obtaining evidence:
What I did:
First, I measured out a 5cm strip of magnesium. Next I measured out 50cm3 of sulphuric acid, using a measuring cylinder, and poured the sulphuric acid into a beaker. Next I took a 5cm magnesium strip, making sure the strip was flat, and dropped it in the all acid solution. As soon I dropped the strip into the acid I started the timer. I then stopped the timer when the magnesium had completely dissolved and recorded the time in my table.
I repeated this 4 more times but I diluted the acid with more water every time. The second time there was 40cm3 of acid and 10cm3 of water, the third time there was 30cm3 of acid and 20cm3 of water, recording my results each time. I continued this until there was 40cm3 of water and 10cm3 of acid in the beaker.
I conducted the experiment a second time to get the most accurate results I could get.
I made no changes to my plan.
Completed table of results:
Equation:
Mg + H2S04 MgS04 + H2
Safety precautions I took:
- I wore an apron at all times.
- I wore goggles at all times.
- Any acid spills that happened, I cleaned it up with a damp cloth to dilute it.
- Chairs and school bags were tucked in under the table.
Observations:
- Chocking gas given off (hydrogen)
- The magnesium strip reacted at the surface.
- The magnesium completely dissolved every time
Interpreting and evaluating:
The best way I can display my results clearly is on a graph.
Line of best fit
Clear patterns:
I noticed in my graphs as the concentration went up the rate of reaction went up.
What I found out:
I found out that in the winter the magnesium statue will corrode more because there will be a bigger concentration of acid rain (sulphuric acid) because more fossil fuels are burnt in the winter.
Also as the concentration of sulphuric acid increases, the rate of erosion increases.
Does my conclusion fit my prediction? :
My prediction was that in the winter the concentration of acid rain will be higher because people will burn more fossil fuels in the winter. The increased concentration will increase the number of collisions, therefore more reactions.
Yes, my conclusion fitted exactly my prediction.
Diagrams and explanations:
Low concentration High concentration
-Magnesium particles (Mg)
-H+ particles
-Low concentration: particles far apart, few collisions, low rate of reaction.
-High concentration: particles more crowed more collisions high rate of reaction.
Was my method the best way to conduct my experiment? :
No, I don’t think my method was the best way to conduct my experiment. A better way would be to use a gas syringe. The gas syringe would measure the amount of gas given off in each reaction. This would give a far more accurate result, to show on my graph. The drawing curve would also smooth out errors.
But the draw backs of using a gas syringe are:
- It is very time consuming.
- More than one person has to conduct the experiment.
- It is more awkward.
If I used the gas syringe my graph would look like this:
Diagram of gas syringe:
Improvements:
If I did the experiment again the improvements I would make would be:
- I would measure out the water and sulphuric acid to a greater degree of accuracy.
- I would make sure the magnesium strip was completely flat when dropping it into the solution.
- I would be more accurate on my timing.
- I would repeat my experiment again to get more accurate results.
Were my results accurate enough? :
Yes, I think my results were accurate because the shapes of my graphs were what I predicted. The rate vs. concentration was proportional on my graph, and time vs. concentration was inversely proportional on my graph.
Results that did not fit the pattern:
In my experiment I got a few results that did not fit the predicted pattern. This may be because of a few things:
- The beaker was not rinsed out properly, so that affected the concentration.
- The magnesium was not cleaned properly.
- There may have been temperature fluctuations.
Are my results good enough to convince other people? :
Yes, I think they are because the results fitted exactly with my predictions, they are straight forward and easy to read, the results and method were based on sound scientific knowledge, the results are reproducible and the there are valid reasons why the magnesium statue corroded.