Investigate how changing the surface area of Calcium carbonate affects the rate of reaction with hydrochloric acid.

AIM:

My aim is to investigate how changing the surface area of Calcium carbonate affects the rate of reaction with hydrochloric acid.

PLAN:

In my experiment I will need the following equipment:

2 conical flasks.
Cotton wool - placed loosely above flask to trap acid spray.
0 - 1000g balance - to weigh and equalize the mass of the marble chips and the powdered marble, to weigh how much mass is lost after reaction.
20cm3 of hydrochloric acid for each flask.
A stop clock - to time the reaction (5:00 minutes).

Safety

I will wear goggles since acids can damage eyes or the pupil cavity if inadvertently squirted at.

When using the acid I will handle it cautiously and with responsibility because acids are very dangerous substances and can cause major skin irritation or burns. Marble chips however small or large can be sometimes inhaled or lodged in bodily organs and orifices like eyes and ears or noses. These dangers should be noted; nevertheless they are unlikely to occur.

Fair testing

To keep it a fair test, the variables need to be kept the same to prevent getting the incorrect results. The acid needs to be kept at a constant room temperature to avoid the marble chips or powdered marble from reacting at a different rate. The size of the marble chips needs to be kept the same because when I do my 1st attempt the chips need to have equal mass and size compared to the 2nd, therefore this will make the test fair. If the marble has a larger surface area than the previous chips the results would be wrong because it has a larger area to act on.

The Hydrochloric acid cannot be used again after the reaction otherwise the acid will be less strong to act on the marble chips.

I will begin my experiment by firstly adding 20cm3 of hydrochloric acid to flask 1 containing the marble chips. As soon as I do this I will immediately start the timer (stop clock). After 5:00 minutes exactly I will stop the timer and record how much mass was lost in that period of time.

Subsequently, I will repeat the same experiment but with powdered marble in place of marble chips.

For each experiment I will repeat 2 times because it allows me to calculate an average rate of reaction and I will also measure my results to the nearest gram. This will make sure that there are no anomalous results and it will increase accuracy. I will not repeat my test more than twice as this is the limit our teacher gave us.

HYPOTHESIS:

I predict that the powdered marble will react faster than ...

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Subsequently, I will repeat the same experiment but with powdered marble in place of marble chips.

HYPOTHESIS:

I predict that the powdered marble will react faster than the marble chips. This is because increasing the surface area increases the chance of the particles hitting the reactant and allows more particles to react with the reactant at once. The larger the surface area of the marble, the greater the number of collisions, and hence the rate of the reaction increases.

Chemical reactions take place by chance. Particles need to collide with enough velocity so that they react. As the surface area is enlarged the particles have a greater surface to react with, accordingly more molecules can react at a time. This means that they are colliding more often and there is a higher chance that the collisions have enough speed to cause a reaction. Since there are more collisions the chemical reaction takes place faster.

EQUATION OF REACTION:

Calcium carbonate + Hydrochloric acid Calcium chloride + water + Carbon dioxide

CaCO3 (s) + 2HCl (aq) CaCL2 (aq) + H20 (l) + CO2 (g)

METHOD:

To make sure the experiment was fair I had to follow the same method every time that is listed underneath.

To start with we placed the marble chips inside the flask and then we weighed it on the balance.

The chips weighed 52.70g to the nearest 2 decimal places. Afterwards, we measured 20cm3 of hydrochloric acid with a measuring cylinder and then we added it to the chips. Instantaneously we started the stop clock. To make sure no spray escaped out of the flask we loosely placed a cotton wool above it.

After the 5:00 minutes were up we stopped the timer. Then we recorded the results to the results chart. Shortly after I had done the 1st attempt I repeated the same procedure again to ensure higher accuracy.

Later on, after I had finished the test with the marble chips, I started my experiment with the exact process but with powdered marble. Then I repeated every step again, like I clarified earlier, to make sure the results are highly exact as possible.

To guarantee our method was safe we followed the safety procedures listed earlier.

DIAGRAM:

Flask 1: Flask 2:

RESULTS CHART:

Time of reaction: 5:00minutes

To calculate the Average Percentage Loss in Mass I added both of the results together and divided it by two. Both results were measured to the nearest 2.d.p because this how accurate the balance was, and our averages were, so we could not write a more accurate result.

Here is an example of how I calculated the Average Percentage Loss in Mass =

5.3 + 5.1 = 10.4

(10.4) / 2 = 5.2

GRAPH:

Time of reaction: 5:00minutes

Analysis:

The graph shows that the larger the surface area of marble the higher the percentage loss in mass.

CONCLUSION:

In this experiment my aim was to investigate how changing the surface area of marble affects the rate of reaction with hydrochloric acid. I recorded how much mass was lost after reacting with 2 different states of marble with the hydrochloric acid. My prediction matched with my results. The graph showing the average percentage loss in mass with different states of marble proves that the higher surface area of marble the faster it will react.

The evidence obtained shows us that surface area is a large factor in determining the rate of reaction. This statement is backed up by the results chart. It clearly illustrates that the higher the surface area the larger amount of mass is lost.

The rate of reaction depends on how often and how hard the reacting particles collide with each other. Particles have to collide in order to react, and they have to collide hard enough as well. This is called “the collision theory”. When the surface area is increased the particles have more area to work on, thus they are going to have more useful collisions which enable them to react more rapidly.

There are other factors that affect the rate of a reaction. They are:

Concentration of reactants:

Concentration means “the pressure”. So if you increase the concentration, there are more particles in the same volume so more collisions are possible every second.

Temperature of reactants:

Temperature increases the rate of a reaction. At the higher temperatures reactant particles move faster and collide more often and more violently. Faster collisions are only caused by increasing the temperature.

Use of catalysts:

Also increases the number of collisions by giving the reacting particles a surface to attach to where they can knock into each other. Catalysts are not used up in a reaction.

These factors affect the number of collisions of reactant particles, and this, in turn, affects the rate of the reaction.

Evaluation:

I think the experiment went very well as I managed to get all the information I needed and safety procedures were followed so no accidents took place or any people were injured which I am very pleased about. I believe that my results are reliable and precise because I repeated my experiment 2 times and then I calculated an average for my results which made it reasonably accurate. The graph proved to me that my predictions were correct, as I didn’t get any anomalous results.

I think that my test was fair because I used equivalent mass of marble and hydrochloric acid for each of my experiments, the same equipment was used, the test took place at equal room temperature (25 degrees Celsius), and the time recordings were exact.

I believe that I could have improved my investigation by maybe repeating the experiment more than twice by taking more readings or I could have included tests on other forms of marble, for example: small marble chips and large marble chips. This would improve the accuracy of our graph which would give us a more distinct and obvious pattern. This will furthermore give additional in depth information concerning the reaction of different sizes of marble with hydrochloric acid and their mass loss.

BIBLIOGRAPHY:

To assist me with my experiment I received information from the following sources:

Letts GCSE Science,

The GCSE Bitesize sites on Internet,

CGP Revision Guides,

Larousse Encyclopedia,

Collins Science,

Longman GCSE Science,

Encyclopedia of Science.