factors affecting the errosion of a magnesium statue

Low surface area        High surface area

The rate of a reaction is also determined by the concentration of the reactants. In most cases, the higher the concentration of the reactants, the faster the reaction. At a low concentration, particles are far apart, have few collisions and a low rate of reaction.

At a high concentration; particles are more cramped, making more collisions and a higher rate of reaction.

        

The time and concentration is inversely proportional and have a negative correlation.

 

The concentration and rate of reaction is directly proportional and have a positive correlation.

These are the two graphs I will plot.

A catalyst is a substance that speeds up a reaction without being used up itself. Some reactions have catalysts that can speed them up, but for many reactions there is no catalyst that works. A catalyst provides a surface on which the reaction can take place. This increases the number of collisions between the particles of the substances that are reacting. A catalyst lowers the activation energy (the minimum amount of energy needed for a reaction to take place). This means that the particles can react with less energy than they needed before the catalyst was added

Activation energy is the minimum energy two particles must posses for a reaction to occur when they collide.

I predict that in summer, it will corrode more than in winter, as 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 and acid rain. Acid rain may have a great effect on the rate of corrosion. 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.

S+02              S02

S02+H20             H2S03

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.

This is the table I will record my results

• 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 conduct the experiment a second time to get the most accurate results I can.

•  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.

• I will keep the temperature the same by conducting the experiment at room temperature
• I will control the surface area by making the magnesium strips the same size and length.
• I will control the catalyst by not using one
• I will conduct the experiment in daylight.

Observations during experiment;

• Chocking gas given off (hydrogen)
• The magnesium strip reacted at the surface.
• The magnesium completely dissolved every time.

What I did;

• 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.

Apparatus used;

1. Beaker
2. Measuring cylinder
3. Magnesium strip
4. Sulphuric acid
5. Apron
6. Goggles
7. Water
8. Timer

        

 

In my graphs as the concentration went up the rate of reaction went up. 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 and as the concentration of sulphuric acid increases the rate of erosion increases.

The Time is inversely proportional therefore giving it a negative correlation. As concentration of acid increases, the time taken decreases

Here I can see that

 the rate is directly

proportional to the

Concentration.

As concentration

 increases,

So does the rate of

the reaction

I predicted that corroding will happen fastest in winter as the concentration of acid rain is higher. My conclusions and results fit my prediction as I thought it would.

This diagram consists of H+ ions and magnesium ions. The H+ ions are bombarding the magnesium ions. The amount of collisions is in few numbers as the concentration of acid is low. This is a proportional reaction.

This diagram also consists of H+ ions and magnesium ions. The H+ ions are also bombarding the magnesium ions. The amount of collisions is high as the concentration of acid is high. This is also a proportional reaction

My method was a reliable way of doing the investigation. I could have, however obtained more accurate results by using a “gas syringe”. But using a gas is more awkward and more complicated, for the many reasons;

• More apparatus is needed.
• More than 1 person is needed.
• Plotting the points.

I would have obtained a graph which looks like the following if I had used a gas syringe during the experiment:

I also could have done more to improve the accuracy of this experiment;

• Ensuring timings are accurate.
• Measuring the volumes of water and sulphuric acid accurately (concentrations are correct).
• Ensuring magnesium strip is placed in sulphuric acid flat.
• Repeating experiment another 1 or 2 times.

In my experiment I had to repeat a few results which did not fit with my other results. Results which did not fit my pattern could have been obtained because the magnesium strip was dirty or not flatly laid out and another was, there could have been temperature fluctuations, beakers were not rinsed out thoroughly or the timer could have been off time on insertion of the magnesium into the sulphuric acid. I found out that the slightest detail between experiments could have made the biggest of differences to the overall result.

I believe that the results I obtained were good enough to convince people of my prediction.

• Other people can understand my results.
• It was based on scientific knowledge.
• It gave reproducible results.
• I proved my prediction.
• My method was straight forward and easy to understand.
• My results gave a valid reason why the statue was corroding.

        

Niall Bradley 12L

Mr Finn