Rate of reaction between limestone marble chips (CaCO3) and Hydrochloric acid (HCL)
In this experiment I will be testing the rate of reaction of marble
chips and acid. The by-product is CO2 and we will be testing how much
CO2 is given off.
The marble chips are made out of limestone (CaCO3) with one of the two
acids available: Hydrochloric (HCL) and Sulphuric (H2SO4)
The factors that could affect the rate of reaction
of my experiment
are as follows:
· Concentration of acid
This could affect the rate of reaction because the higher the
concentration of the acid then the more acid particles per 40cm3 so
more collisions per second and then there will be more successful
collisions per second.
· Temperature of the acid
If the starting temperature of the acid is different each time the
speed at which the acid particles collide with the marble chips
increase more the higher the temperature goes. This means the acid
particles move with more energy, which means they will collide with
the marble with more energy, which will give more successful
collisions per second.
· Surface area of the marble chips
If the marble had a bigger surface area each time the experiment was
done, then the acid particles will have a bigger area to collide with,
so more collisions will occur every second and the more collisions per
second than the more successful collisions per second.
· Type of acid used
If you changed the type of acid then the rate of reaction would
change. Hydrochloric, Sulphuric all would produce a different rate of
reaction, so if I do change the type of acid then all three kinds
would produce a different set of results.
All of these factors will change the rate of reaction because of the
Collision Theory. This is a theory that is used to predict the rate of
a reaction. The Collision Theory is based on the idea that for a
chemical reaction to take place, it is necessary for the reacting
particles to collide with each other with enough energy to break or
form new bonds between the other particles, which is called a
successful collision. If when they collide and they do not have enough
energy to break or form new bonds then they will simple bounce of each
other, causing an unsuccessful collision.
I have chosen to use the concentration of the acid as my factor that I
will change. I chose this because several different concentrations can
be made up before the experiment I will be able to make them
There will be several different concentrations of acid, which will
give me a wide range of results, which will be reliable and
I have done some experiments testing out the two acids. We have tested
the two reactions to see how much CO2 is given if we counted the
amount of bubbles in one minute, as at the start as we didn’t need to
be deadly accurate. This will give us suitable information for a
From my preliminary work I have decided to use hydrochloric acid
reacts for a suitable amount of time in order for us to make reliable
results. The hydrochloric makes far more CO2 than sulphuric as it only
reacts for about 15 seconds creating a very little amount of bubbles;
this is because the calcium sulphate forms a layer over the CaCO3,
which stops the reaction making the CaCO3 impermeable.
So therefore I have chosen to use Hydrochloric acid with medium size
chips, as the results would be at a very suitable range with these two
The reaction I am doing is: CaCO3 + 2HCL à CaCl2 + CO2 +H2O
I will be collecting over water in the following set-up of my
1. I will set up my experiment as above.
2. I will put 40ml of 2 molar HCL into the side arm flask.
3. I will measure out 2g (0.4 leverage either way) of marble chips
4. I will put the marble chips into the side arm flask and start the
5. Every 30secs I will take a reading of the volume of CO2 given off
and record it in my table.
6. Restart experiment with different molar of acid E.g. 1.5M, 1.0M,
O.5M and 0M.
7. Repeat all molars
My prediction is that the higher the concentration of the acid then
the higher the rate of the reaction will be. I am saying this because
of the collision theory. The higher the concentration of acid then the
higher the number of acid particles present per 40cm3 of acid. This
means that there will be more collisions per second, which means there
will be more successful collisions per second, so the rate of reaction
If I double the concentration of the acid from 1M hydrochloric acid to
2M hydrochloric acid then I will expect to see the rate of the
reaction double. This is because there are twice as many acid
particles in 2M hydrochloric acid than in 1M hydrochloric acid, so
there will be twice the amount of collisions per second and because
there are twice the amount of collisions per second then there will be
twice as many successful collisions per second, increasing the rate of
From my prelim work it would be suitable to take a reading every 30
secs and gain a suitable graph and firm conclusions.
In order to keep my experiment a fair test I will have to make sure
that I keep the following factors the same:
· Starting temperature of the acid
· Volume of acid used (cubic centimetres)
· size of magnesium
I will also have to make sure that the gas syringe is correctly
connected and that it is placed quickly and tightly enough so that no
hydrogen gas escapes.
Trends and patterns
From my graph all molars present a straight line this would indicate a
doubling of the rate of reaction for all molars but because the
straight line shows as every 30-second reading it doubles. A straight
line shows a constant increase and in this case it is doubling.
My results table and graph show me that when I increase the
concentration of the hydrochloric acid, the initial rate of reaction
Altogether I tested 5 different concentrations of hydrochloric acid.
0.0M, which was the lowest concentration of acid that I used, there
was no reaction. 2.0M hydrochloric acid, which was the highest
concentration that I used, produced the fasted rate of reaction. I
repeated all 5 concentrations twice to be sure that they were reliable
results and in all cases the higher the concentration the higher the
rate of reaction. I had stated this in my prediction.
I also stated in my prediction that if I doubled the concentration
from 1M to 2M hydrochloric acid then the rate of reaction will also
double. I have discovered that this is the case as see below it
approximately doubles from 0.31 to 0.66.
Molar/time (secs) Rate of reaction (cm3/s)
As you can see from this table as the concentration doubles then the
rate of reaction approximately doubles.
I therefore conclude that:
1. The initial rate of reaction increase as the concentration of the
2. There is a twofold increase in the rate of reaction as the
The method I used was good but it could have been better the results
could have been made more accurate and reliable by making sure the
bung didn’t stick to the sides after lots of testing and therefore
letting gas out.
Improvements to my experiment are that I could stop the bung sticking
by applying a thin coating of Vaseline to it. Also we blocked the pip
by accident this aloud an anomalous result but we re-done the test and
get rid of the anomalous result. Any anomalous results were rid off by
Was I precise in my measurements?
I feel that I was precise and accurate in recording measurements.
I measured the acid accurately by measuring the acid when the bottom
of the liquid touched the exact amount I needed.
I accurately measured the volume of gas evolved to the nearest .5cm3.
I accurately measure the time that had elapsed to the nearest second
with the stop clock.
Did I take enough readings?
Not enough concentrations were used for a good graph. I should have
used concentration 3M acid ought to have been done but it was not
known then that it was necessary and required.
The results that I did collect were reliable as I repeated the
experiments twice to obtain good average results. My results were not
only reliable they were reproducible. The results I produced were
reliable enough to base my conclusions the experiment was successful
as a whole but had errors the experiment could be done again and my
conclusions would still be the same although the figures would be more
I could use sulphuric acid. This is a dibasic acid and its molecular
build-up is H2SO4 and hydrochloric acid is 2HCL, because of this I
would obtain different results. I could also use phosphoric acid,
which is a tribasic acid, and its molecular build-up is H3PO4, I would
also obtain different results if I used this type of acid. Nitric acid
is a monobasic acid but its molecular build-up is HNO3, which is very
similar to the molecular build-up of hydrochloric acid so the results
that I would obtain from using this acid would be similar to the ones
I already have, so I would not use this for any further experiments.
The reason I could use a different type of acid for any further work
is to find if the is a difference between them if their molecular
build up is different.
I also could improve this experiment by making sure the surface area
was the same. my surface areas where the same approximately but I
could have made this more accurate by using cubic chips where the
surface areas where known. This way it will make the example eevn more
accurate than it was.
I obtained most of the information that I needed for my experiment
form my teacher and exercise book. I also obtained information from
several science textbooks and computer encyclopaedias. I obtained a
small amount of information from the Internet