The Effect of Concentration on the Rate of Decomposition of Calcium Carbonate.

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The Effect of Concentration on the Rate of Decomposition of Calcium Carbonate.

PLAN

I planned my experiment based on the scientific knowledge I already have: If I increase the concentration the rate of reaction increases. This is because the higher the concentration, the more liquid (acid) particles there are in the same volume, to collide and react with the solid (calcium carbonate) particles. Therefore the rate of reaction increases. Basically the probability of the particles colliding and reacting is increased, when the concentration is increased.

E.g.;

Lower concentration Higher concentration

Prediction:

I believe that the rate of reaction will increase with increase in concentration. This is because as explained above. The higher the concentration, the more liquid (acid) particles there are in the same volume, to react with the solid (calcium carbonate) particles. Therefore the rate of reaction increases.

Basically, at higher concentrations, there are more molecules per litre, so there will be more collisions, so the reaction rate should be higher at the same temperature. Doubling the concentration should double the reaction rate. However for some reactions, the rate may be proportional to the concentration squared. For some reactions it can even be proportional to the concentration to the power 1.5

The Kinetic Rate Law defines the relationship between concentration and reaction rates. According to the law, the rate is directly proportional to the molar concentrations of each reactant in the rate-determining step of the reaction mechanism; each raised to a power equal to their rate order. The Rate of a chemical reaction is equal to a rate constant multiplied by the molar concentration of each reactant raised to the power equal to the rate order. For example if we have a chemical process defined in the following manner:

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Continuation

A + B ----> C

According to the Rate Law:

Rate = k [A]m [B]n

where:

k = rate constant

m = rate order in respect to A

n = rate order in respect to B (http://edie.cprost.sfu.ca/~rhlogan)

Preliminary Plan

Measurements I chose:

Size of calcium carbonate: Medium

Concentration values of acid: 50:0

40:10

30:20

20:30

Mass of calcium carbonate: 10.00g

Temperature of Hydrochloric acid: Constant

Preliminary Method:

I placed the 10.00 grams of calcium carbonate in to a conical flask (as shown above). I then added the amount of acid and water I had chosen. I quickly replaced the rubber bung on top of the conical flask in order to let out as little gas (co2) given off, out of the flask as not to hinder the accuracy of the results. As soon as I had done this I started the stopwatch. A tube was attached to the rubber bung (as shown above) which allowed the co2 to flow to a gas syringe where I could measure the amount of gas collected. I recorded the volume of gas collected in the gas syringe every ten seconds. I recorded it every ten seconds in order to get an accurate rate of reaction throughout the experiment. During the experiment I kept the Hydrochloric acid and water the same temperature as not to introduce another limiting factor (an increase in temperature increases the rate of reaction). I also used the same amount and surface area of calcium carbonate in order not to introduce another limiting factor which would make the results unreliable (the larger the surface area the quicker the rate of reaction).
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Preliminary Results:

Time

Concentration of acid

50.00

40.10

30.20

20.30

0.40

Molar =

0.8

0.6

0.4

0.2

Experiment 1

Experiment 1

Experiment 1

Experiment 1

Experiment 1

0

5

4

3.5

2

20

9

6

5.5

2

2.5

30

4

9.5

0

3

3

40

21

5

4

3.5

3

50

27.5

7

8.5
...

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