Rates Of Reaction


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.


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 reactionCalcium 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 ApparatusImportant 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
(Molar)

Amount of Hydrochloric Acid (HCL) in ml Amount of Water (H2O) in ml0.5 M8 ml32 ml1.0 M16 ml24 ml1.5 M24 ml16 ml2.0 M32 ml8 ml2.5 M40 ml0 ml Preliminary experimentI 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 1)


Gas volume (test 2)


Gas volume (Test 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