Investigating the Rate of Reaction Between Magnesium Ribbon and Hydrochloric Acid
Length: 1726 words (4.9 double-spaced pages)
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To find out the rate in which magnesium ribbon dissolves in different
molars of hydrochloric acid, and which factors affect the rate of
The 'Collision Theory' says that particles can only react if they
collide with enough energy for the reaction to take place. As well as
the collision theory there are also other factors that will effect how
quickly and effectively the reactions take place.
The four factors that effect the rate of a chemical reaction are:
CONCENTRATION OF ACID,
SURFACE AREA OF THE REACTANT
and USE OF A CATALYST.
The higher the temperature of the solution, the faster the rate of
reaction, and vice versa. This is because as the solution heats up the
particles gain energy and begin to move faster and with more energy.
This causes more successful collisions per minute and consequently a
faster rate of reaction.
We carried out an experiment in lesson, which involved placing marble
pieces in hydrochloric acid. We altered the temperature of the acid
and recorded the speed in which the marble dissolved in the different
After repeating the experiment several times, we found that the higher
the temperature of the acid the faster the marble reacted and
consequently dissolved. This is, as I said above, because the acid
particles have more energy to move around and they collide with more
energy, increasing the rate of reaction.
HOT = FAST COLD = SLOW
The concentration of the acid will effect the rate of reaction. This
is because there are more particles of acid to collide with the metal
particles. The higher the concentration of acid the faster the rate of
reaction will be, and vice verse.
We carried out an experiment as a class to investigate how
concentration effected the rate of reaction. We altered the ratio of
acid:water in 40ml of solution and added marble chips to the acid. We
recorded how long it took to collect 30ml of carbon dioxide from the
gas given off from the reaction. We found that the higher the
concentration of acid, the less time it took to collect the carbon
HIGH CONCENTRATION LOW CONCENTRATION
s FAST SLOW
The surface area of the reactant causes the rate of reaction to alter
because the larger the surface area, the more points of contact there
are for the acid to react with. A powder has a much larger surface
area than a large chip or strip of the same mass; more of the reactant
is exposed to the acid creating a much faster rate of reaction. The
frequency of collisions is increased therefore the more collisions
taking place the faster the reaction will be.
During a lesson we carried out an experiment to investigate which
reacted faster, large or small marble chips. We placed the different
size chips and the acid in two measuring cylinders and placed them on
weighing scales. At the start they both weighed the same as we
measured out the same weight of chips and used the same amount of
acid. At consistent time intervals we recorded the loss in weight of
the two measuring cylinders, and by the end of the experiment it was
clear that the smaller chips reacted faster than the large chips. This
was because the small chips had more points of contact for the acid to
react with, causing the reaction to take place much faster.
LARGE SURFACE AREA SMALL SURFACE AREA
Use Of A Suitable Catalyst
The use of a catalyst will also effect the rate of the reaction. A
catalyst lowers the activation energy of a reaction, this means that
if the particles collide with only a moderate energy, they will still
react. This increases the chance of a successful collision, which
increases the rate of the reaction. Also some catalysts work because
one of the particles is attached to a surface, which makes a collision
CATALYST PRESENT NO CATALYST
The factor I am going to investigate is the CONCENTRATION OF ACID. I
will carry out different experiments varying the molarity of the acid
and recording my findings.
I predict that the stronger the acid the faster the reaction will take
place due to there being more particles available to react with the
To ensure my tests are fair I will have to keep all of the other
factors the same. For instance I will have to check that the strength
of the acid remains the same, although I will be altering the
concentration of the acid by adding varied amounts of water to it.
Also I will maintain a constant temperature of the solution to prevent
the reaction taking place faster or slower than the others will.
The Magnesium ribbon pieces will all have to have the same surface
area to again ensure the test is fair. I will make the difference in
molarities consistently even for it to remain a reliable experiment. I
will start with a high molarity of acid and then reduce it in
consistent intervals until I feel I have enough data to prove my
prediction right or wrong. I will ensure I have enough to produce an
To prevent injuring myself I will have to handle the acid carefully,
as it is extremely corrosive. I will also wear goggles to prevent any
acid splashing into my eyes during the experiment. Also care will have
to be taken with the glass boiling tubes.
10 boiling tubes Magnesium ribbon
1 boiling tube rack Ruler
1 bottle 2m HCL acid Scissors
Beaker of water Sticky labels
2 measuring cylinders Goggles
¨ Firstly I collected all of the above equipment and prepared my work
surface for the start of the experiment. I put on my goggles before
collecting the acid and continued to wear the goggles until I had
stopped handling the acid at the end of the experiments.
¨ I placed all of the boiling tubes in the rack and stuck labels
around them so I could identify each tube accurately, for example
10:0, 9:1, 8:2 etc which represents the ratio of acid to water.
¨ Then, using two separate measuring cylinders, one for acid and one
for the water, I measured out accurately the solutions of acid:water.
¨ When I had done this I cut the magnesium ribbon to lengths of 2 cm
trying to maintain a high level of accuracy.
¨ Next, I placed a piece of the ribbon inside the boiling tubes one by
one, timing how long it took for the ribbon to dissolve and recording
my findings for each tube before moving to the next consecutive tube.
¨ I repeated the experiments three times for each tube, replacing the
acid after each test to ensure the acid was at its most reactive
¨ I then used the results to get a list of average times and I plotted
a graph of the results.
Here is a table containing the times I recorded, they are in minutes
and rounded to 2 decimal places. The ratios of acid to water are
measured in millilitres.
Ratio of acid:water
1 2 3
No reaction after 10 minutes
I decided to calculate the average time, as it will be easier to plot
a graph using these times.
I have included a table of the average times in minutes. I will not
include the 0:10 as there was no reaction, therefore no time to
Again the ratios are measured in millilitres and the times are in
minutes. They are to two decimal places, but they could be rounded to
1 decimal place for ease but they will not be as accurate.
Ratio of acid:water
Average reaction time
I have included the graph to show these results.
My results show that the higher the concentration of acid, the faster
the reaction takes place. This is because there are more acid
particles to collide with the metal particles in the given volume,
which in turn causes the reaction to take place much faster than it
does in the pure water solution where no reaction took place at all.
If I refer back to the Collision Theory you can see that this idea is
clearly correct. The particles collided with more energy in the higher
concentrations of acid, compared to the mostly water solutions in
which particles had little or no energy to move or collide. As I
watered down the solution it took increasingly longer for the reaction
to take place. The hydrogen bubbles that will have formed around the
magnesium strip will have effected the amount of acid getting to the
ribbon. These would have acted as a protective layer limiting how much
acid gets through to react with the magnesium.
My prediction was correct. The higher the concentration of the acid
the faster the reaction did take place. There are more particles of
acid to react with the magnesium ribbon, consequently speeding up the
rate of the reaction.
It is clear that anomalies will occur in experiments like these
because there is room for inaccuracy. As you can see on my
average-time table there is an anomaly. This could be because of many
reasons. If I were to do this again I would alter certain aspects of
my experiments. I would ensure that the magnesium ribbon was exactly
the same in each tube, as due to the short lessons it was not always
possible to ensure that it was exactly the same. It could have been
cut from a different strip of ribbon, which could alter the weight of
it. Also I tried to cut the strip as close to 2cm as possible, but
again due to the lack of highly specialised cutting equipment they may
not have been as accurate as they could have been, or as I would have
The strip could have also been of different thickness, which again
would have altered the results slightly. If the strip was quite old it
may not have been as reactive as it would have been previously when
So if I were to do these experiments again and have any equipment I
liked to carry them out, I would use a highly accurate laser cutter to
cut the ribbon with little or no room for inaccuracy. Maybe I could
also use very sensitive weighing equipment to weigh the ribbon to
check it was all the same, and then alter it accordingly. The acid may
have also been older, again reducing its reactivity, so I would use
new acid. The acid may have been form a different bottle, I did ask my
teacher, but she was not 100% positive that it was although she did
not think they had more than one bottle. If it had have been from a
different bottle this could again have been the cause for my anomalous
When measuring out the acid into the measuring cylinder, I had to use
my eye to judge how much was in the cylinder. This again may have been
inaccurate, as I couldn't check that I used exactly the right amount
each time. As I repeated the results it also not certain that I used
the same amount for the same tubes in each repeat.
Other factors, although I tried to prevent this, could have maybe
affected my experiments. If the temperature in the room was higher in
one lesson than in the other, the particles in the acid would have had
more energy and so caused the reaction to take place faster. If the
magnesium ribbon pieces were not exactly the same some would have had
a smaller/ larger surface area causing the rate of reaction to be
faster/slower which would nave had an effect on my results.
Although I did get some anomalous results it is clear that I have
proved my prediction to be correct. The results were sufficient to
prove my theory, but if I were to do the experiments again I would
repeat them more than three times to get a higher level of accuracy.
Along with access to more skilled equipment and more repeats, I feel
that my results would or could be flawless and highly accurate.
Overall my experiments went well and I feel I achieved the results I
set out to obtain.