All of these factors will change the rate of reaction. Chemical reactions take place by chance. Particles need to collide with enough velocity so that they react. As the temperature is increased the particles move faster since they have more energy. This means that they are colliding more often and more of the collisions have enough velocity to cause a reaction. Since there are more collisions the chemical reaction takes place faster.
The aim of this investigation is to find out how long it takes before the magnesium strips are completely eroded away by the hydrochloric acid.
I decided that before I began it would be best if I got some background information regarding magnesium and hydrochloric acid.
Magnesium
Magnesium is a silvery white metallic element that is relatively un-reactive. It is in group 2 of the periodic table. Magnesium is one of the alkaline earth metals. The atomic number of magnesium is 12.
The metal was first isolated by the British chemist Sir Humphry Davy in 1808, is obtained today chiefly by electrolysis of fused magnesium chloride. Magnesium is malleable and ductile when heated. With the exception of beryllium it is the lightest metal that remains stable under ordinary conditions. The metal is not attacked by oxygen, water, or alkalies at room temperature; it reacts with acids. When heated to about 800° C, it reacts with oxygen and emits a brilliant white light. Magnesium melts at about 649° C, boils at about 1107° C, and has a specific gravity of 1.74; the atomic weight of magnesium is 24.305.
Hydrochloric Acid
Hydrochloric acid is a strong colorless acid formed when hydrogen chloride gas dissociates in water. It is often used in industrial and laboratory processes. Hydrochloric is also produced in the stomach, where it initiates the digestion of proteins.
Plan
In my experiment I am going to use 0.2g of magnesium divided equally by 4. The volume of hydrochloric acid that I am going to use is 25ml. I am going to measure the rate of the reaction by collecting the hydrogen gas that is produced during the experiment in an upside down measuring cylinder, which is full of water and also placed in a container of water. The gas that is produced will pass through a delivery tube which is stuck into a rubber bung in a conical flask where the initial reaction will begin to take place. I will quickly drop the length of magnesium into the flask and put the delivery tube under the upside down measuring cylinder. I will then start the stop watch, then I will record the volume of gas produced every 20 seconds until I can see that the reaction is no longer continuing.
Fair Testing
In order to keep my investigation fair I will have to ensure that I keep the following the same:
- Length of magnesium
- Surface area of the magnesium
- Volume of acid used
- Starting temperature of the acid
I think that it would also be a good idea if I made sure that all the equipment is in use properly. For example the bung is in the flask correctly, as this would affect the results.
Changes
Throughout each of the experiment I am going to change the concentration of the hydrochloric acid.
Apparatus
- Conical flask
- water
- magnesium ribbon
- Ruler
- Safety glasses
- Measuring cylinder
- delivery tube
- plastic tub
- Hydrochloric acid
- Stop watch
Safety
There are some safety aspects throughout the investigation that I need to follow in order to keep myself safe. These include:
- Wearing safety goggles when I am using hydrochloric acid
- Care when using glass equipment, if care is no taken, glass can be broke and skin can be cut
- The disposal of the reagents and chemicals needs to be done safely
- Care needs to be taken when returning equipment, especially glass equipment and acids
Results
1st experiment
2nd experiment
3rd experiment
4th experiment
Conclusion
It was very noticeable, when I looked at the results that the more concentrated acid had a faster rate of reaction than the less concentrated acid. This was probably because there are more particles in a concentrated acid and as a result more collisions will occur.
I decided that one of the best ways in which to present my results would be a graph.
The graph shows that my original expectation was correct: that the rate of the reaction will be faster with the higher concentration of acid there is. In a higher concentration there are more acid particles to react with the magnesium ribbon and therefore the magnesium is eaten away quicker.
This shows me that by changing what seems to be a small factor at the time, it can result in a significant effect.
Looking at the set of results obtained, you can see clearly that they all follow the expected pattern. This pattern suggests that the reaction rate increase when the concentration of the acid increases because if you increase the concentration of the acid you are introducing more particles into the reaction which will in turn produce a faster reaction because there will be more collisions between the particles which is what increases the reaction rate.
The evidence I have been able to gather from this investigation seems to lead to a quite firm conclusion. I might not have been able to find the exact speed of the reactions but the pattern seems to be correct as I have repeated readings four times and seem to have a similar result for each of the repeated readings.
I used the variable of concentration, which seemed to be of a good choice as it would show the results of how more acid molecules reacting with magnesium, would result in a faster reaction.
Evaluation
There will always be ways in which you can improve your investigations and the same thing goes for the investigation which I carried out.
The problems that occurred throughout the investigation for me were;
- Pouring the exact amount of hydrochloric acid
- Time scale in which we was on
If I was to repeat this investigation I would try to ensure that I do it as accurately and thoroughly as possible.
