The Rate of Reaction Between Calcium Carbonate and Hydrochloric Acid Aim
To investigate whether the rate of reaction between calcium carbonate
and hydrochloric acid increases when the molar concentrate of
hydrochloric acid is increased.
occurs naturally as limestone, chalk and marble in
rocks. Its chemical formula is CaCO3 (s). Here are its properties:
1. It cannot be dissolved in water.
2. If reacted with acid it forms a salt, carbon dioxide and water.
3. If heated, it breaks down to form carbon dioxide and an oxide.
is formed by dissolving hydrogen chloride in water.
Its formula is HCL(aq). It is like most acids in its properties.
* It reacts with metals to give hydrogen and salts/chlorides.
* It reacts with metal oxides and hydroxides to form chlorides and
* It reacts with carbonates to form chlorides, water, and carbon
The word and chemical equation for the reaction between these two
[IMAGE]Calcium Carbonate+hydrochloric acid Calcium
[IMAGE]CaCO3(s) + 2HCl(aq) CaCl2(aq) + H2O(l) + CO2(g)
For any reaction to occur, separate reactant particles must collide.
There are several factors affecting the rate at which these reactions
* CONCENTRATION: if the concentration of a reactant is increased,
then so will the rate of the reaction. This can be explained by
the fact that if the concentration increases, so does the amount
of reactant particles in the same volume and therefore more
collisions are able to happen.
* TEMPERATURE: when the temperature in a reaction is increased, the
rate of reaction
also increases. This is because the reactant
particles have more thermal energy from the heat and so travel
faster, collide more often with other particles and collide more
* SURFACE AREA: if the total surface area of a solid is increased,
there is an increase in the amount of particles in contact with
the reactant particles in solution. Therefore more reactions are
possible between the two reactants.
* CATALYSTS: a catalyst is a substance that helps increase the rate
of a chemical reaction, but remains chemically unchanged itself.
So if a catalyst is present while a reaction is occurring, the
speed of the reaction will increase.
The independent variables that could be changed in this experiment to
investigate the rate of reactions between the two reactants are:
* Surface area.
I have explained in my background information what effects these
variables have on a reaction and I have chosen to investigate whether
the concentration of hydrochloric acid I use affects the rate of
The variables that I will keep the same to make the test fair are:
* The total surface area of the chips of calcium carbonate I will
use in the reaction. However this will vary slightly as not all
the chips are exactly the same size.
* Every experiment will be carried out at room temperature so the
reactant particles do not have more energy in one experiment than
* I will keep the mass of the amount of chips I put in the hydrogen
chloride solution the same.
* I will use the same volume of solution for each experiment.
The dependent variable I will be measuring is the amount of CO2 gas
produced by the reaction in cm3. The more gas that is produced in the
reaction, the faster the reaction is occurring.
I think that as the concentration of hydrochloric acid solution
increases, then so will the rate of the reaction, therefore more
carbon dioxide gas will be given off in the reaction. I have based
this hypothesis on my scientific knowledge of rates of reaction. It
has been proven that increasing the concentration of reactants will
increase the rate of a reaction, as there are more particles of a
reactant in the same volume allowing for more collisions every second.
I am confident that the results I gain from this experiment will fully
support this hypothesis. I will be carrying out this experiment for as
long as it takes for the gas syringe to fill up and here is my
prediction of what the graph to show my results will look like:
This graph shows that as the concentration increases, so does the
amount of carbon dioxide gas produced in the reaction.
I will also draw up a graph to show how the rate of the reaction
changes over time, however I don't think the rate will change that
much as I am only carrying the reaction out over a small period of
I do not think that over 1 minute the rate will change much if at all.
However, if I was to continue this experiment for longer than 1minute,
i.e. 10 minutes, I think the graph that would be produced would look
The yellow circle shows the first stage of the graph, the reaction is
taking place very quickly and at the same rate, this is what I expect
to see in the first minute.
The blue circle shows the second stage of the graph, in this stage the
reaction is beginning to slow down as the mass of the calcium
carbonate has decreased as a lot has already been used up in the
reaction so there is less of one reactant.
The red circle shows the third stage of the graph, in this stage I
think that all the calcium carbonate will have been used up and so the
amount of carbon dioxide gas produced will remain the same.
As I will be using acid in this experiment I will be very careful
handling it and will wear a lab coat to protect my skin and clothes
and goggled to protect my eyes. Glasses are not good enough for this
experiment as solution may still get splashed on my eyes as there is
no protection on the side of the glasses.
Equipment: 1x boiling tube, 1x retort stand, 1x retort stand clamp, 1x
test tube rack/holder, 1x gas syringe (100 cm3), 1x gas syringe to
test tube connector, 300x medium size calcium carbonate chips, 150cm3
of each molar of hydrochloric acid solutions (0.2, 0.4, 0.6, 0.8, 1.0,
1.2, 1.4, 1.6, 1.8, 2.0), 1x stop clock.
1. Set up the retort stand and clamp on your worktop.
2. Place the gas syringe in the clamp and attach the connector to
its nozzle, making sure the plunger of the gas syringe is all the
3. Fill one boiling tube with 50c m3 of the first molar solution you
will be testing.
4. Place it in the test tube rack/holder.
5. When you are ready with the stop clock, put 10 of the calcium
carbonate chips into the solution, quickly connect the syringe to
the boiling tube and press start on the stop clock. (This step
must be done quickly yet carefully!)
6. After every 10 seconds from 0, read where the plunger is in the
gas syringe and record the result in a table.
7. At 60 seconds take the last reading and stop the clock and
disconnect the boiling tube and the syringe.
8. Pour the contents of the boiling tube into a sieve, leaving al
the marble chips behind.
9. Wash the chips and the boiling tube in water. (if the boiling
tube is washed, it can be used again for the experiment)
10. Repeat the steps 4-9 again 2 more times with the same molar,
record the results then repeat steps 4-9 3 more times with a
different molar solution. You must repeat this experiment 3 times
with every molar solution to get an average result and get rid of
This table shows the results from my experiment:
Volume of carbon dioxide gas produced by each molar concentration (ml)
My results table shows that as the concentration of the hydrogen
chloride solution increases, so does that rate at which the reaction
occurs, therefore supporting my hypothesis. It also shows on some
results my theory that as time went on, and then the rate of reaction
would slow down. This can best be seen in the results 1.2 and 1.4
molar. I have also drawn up a graph comparing how much carbon dioxide
gas was collected 50 seconds after the reaction had started:
[IMAGE]The red line shows what I think is the line of best fit. It
shows a positive relationship with the amount of carbon dioxide gas
produced by the reaction and the molar of the solution. This is what I
predicted would happen in my hypothesis and I am glad that the results
have supported my prediction.
Using knowledge from my prediction and background I can explain this
correlation of results. As the molar of the solution increases, so
does the amount of active reactants in the solution. When there is
more of one reactant, more collisions will occur increasing the rate
Judging the experiment by my results and the safety precautions when
carrying out the procedure, I would say my experiment went well. There
were no serious anomalies, only results a small way off the mark I
expected them to be as you can see in the graph from my first
experiment (0.2 molar). Overall though I thought the results were good
as they strongly supported my hypothesis.
I think the method I used to gather my results was very effective in
obtaining good results and was very hazard free. It was also very easy
to set up and carry out. If I was to repeat the experiment I would use
the same method. However in the higher molar tests, the amount of
carbon dioxide gas went off the scale and so I would use a larger
syringe so the results could carry on for longer. I would also use a
different container other than a boiling tube so more of the calcium
carbonate would be in contact with the solution.
There were no problems that occurred during the experiment to do with
safety or with gathering results so I believe the experiment went