Aim: To investigate the effect of the concentration of Hydrochloric acid
on the rate of reaction between Hydrochloric acid and Calcium Carbonate.


Background:The rate of reactions between two substances is dependent on
many factors or variables:
1. Change in temperature
2. Surface area of solid substance,
3. Concentration of the acid,
4. Volume of Acid used.

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While doing my experiment, I must remember to keep all of my variables the
same. This will make it a fair test. For example, if I shake the conical at
the beginning of the experiment, I then need to do it for all of my
experiments.


Chemical and word equation for reaction
Calcium Carbonate + Hydrochloric acid ———–} Calcium carbonate +
Water +
asg
Carbon Dioxide.


CaCO3 + 2HCL ——–} CaCL2+ CO2 + H2O
I have decided that the variable I will use will be concentration of
Hydrochloric acid (HCL). This will be reacted with Calcium Carbonate
(CaCO3). I feel that the other variables will be much harder to get a good
set of results from. For example keeping the temperature at a constant is
extremely hard to accomplish using a Bunsen burner, and the school does not
have enough heat tubs for us to use. Also calculating the surface area of
the calcium carbonate chips would be extremely difficult as they’re not all
the same size.



Diagram of Apparatus

Important information
. I will be reacting all of my various concentrations with 3g of medium
sized calcium carbonate chips.


. I will be repeating the experiment 3 times. I’m doing this because I can
then find an average of the 2 sets of results, which look most reliable
and plot a line graph.


The Experiment
First of all I will get my own jar of 2.5M Hydrochloric acid, from this I
can the make all of my concentrations. 2M, 1.5M, 1.0mM 0.5M. This avoids
the 2.5M concentration changing.



To make my concentrations I should follow this table.


|Concentration|Amount of Hydrochloric|Amount of Water (H2O) |
|(Molar)|Acid (HCL) in ml|in ml|
|0.5 M|8 ml|32 ml|
|1.0 M|16 ml|24 ml|
|1.5 M|24 ml|16 ml|
|2.0 M|32 ml|8 ml|
|2.5 M|40 ml|0 ml|
||||
Preliminary experiment
I will then start my Preliminary experiments. This is to get the time scale
rite. My first time scale was wrong. I timed the rate of reaction every 30
seconds for 3minutes; this only gave me 3 readings. As the 2.5M
Hydrochloric acid reacted very quickly with the Calcium Carbonate chips.


Preliminary Experiment Table of Results
|Time (seconds) |Gas volume (test|Gas volume (test|Gas volume (Test|
||1) |2) |3) |
|30 |30 |29 |-|
|60 |65 |70 |-|
|90 |102 |97 |-|
|120 |-|-|-|
|150 |-|-|-|
I then changed my time scale. This time, I took a reading of the reaction
every 10 seconds for 3minutes. This gave me at least 6-8 results. From the
data I’ve collected from my experiments. I will draw a line graph to show
the rates of reactions. From this I can see whether concentration does
affect, the rate at which calcium carbonate dissolves.



Prediction
Providing that the variables of my experiment remain constant I would
expect that the amount of CO2 given off would be directly proportional to
the change in concentration. I predict that by increasing the
concentration that the amount of Carbon Dioxide will also be increased. I
think that by doubling my concentration the amount of gas will be doubled.

This is due to the collision theory. However, depending on the
conditions, only a small fraction of the collisions are effective in
producing a reaction. There are several constraints. In order for a
reaction to occur, bonds initially are broken, which requires energy. This
energy depends on the type of the reaction and comes from the kinetic
energies that the molecules possess before the collision. It is called the
activation energy. Increasing the temperature increases the kinetic
energies and more collisions will occur. In addition, at a higher
temperature a greater number of the reacting molecules might possess energy
equal to or greater than the activation energy. However the molecules must
also collide in a specific direction, called the satiric factor in order
for a reaction to occur. A reaction will only be successful, if the
collision has enough energy to be either equal to or greater than the
activation energy and if the orientation of the collision allows for
correct bond formation. As I’ am not testing temperature. The morality
which I’ am testing will affect the rate of reaction. The increase in
concentration causes there to be more molecules in the solution, which
means that collisions are more likely to occur. This increase in
collisions will mean that the reaction will reach its optimum rate faster.

Therefore the rate of reaction is faster.