Investigate the rate of reaction between different concentrations of hydrochloric acid with metal carbonates using calcium carbonate as the example.

• They have a smaller surface area than powder, making the timing much easier.
• They are easier to measure, which will help the accuracy of the experiment.

Preliminary Work

During my preliminary work I tested the highest and the lowest and highest concentrations, I did this to find the shortest and longest times it would take to do the experiment. The results obtained are shown below:

These results have confirmed that I will use the quantities shown in the concentrations table above.

Reliable Test

The method I will use to make sure that my results are reliable is to test each concentration three times. This will then give me three results for each concentration, after this I will calculate my average or mean time. The average will give me a good overall reliable result for my experiment.

Fair Testing

The ways in which I will make sure that my experiment is conducted in a fair and affective way are as follows:

1. Start timing each concentration as soon as the lid is on. This will decrease the chances of any anomalous results appearing.
2. Rinse and dry out the conical flask after each experiment. This will help to make sure that each concentration is timed in the same conditions as the last, adding to the reliability of the practical.
3. After each experiment I will re-set the amount of water in the measuring cylinder to 100cm3. This is a basic thing to remember but also a very important one too. If this is not done then that particular experiment is made pointless.
4. I will use the same amount of Calcium Carbonate in each experiment (5 grams).
5. The size of the granules will stay the same in each experiment.
6. The temperature will be constant in each experiment as it will be at room temperature.
7. The total volume of the hydrochloric acid and the water will stay the same in each experiment.  

Safety

The precautions that must be taken to make sure I carry out the experiment in a safe environment are:

1. Wear safety goggles; this will stop the chances of any of the substances involved in the practical coming into contact with the eyes and resulting in irritation.
2. Wear an apron; this will decrease the chance of any harm being done should a spillage occur. It also prevents damage being done to clothing.
3. When handling glass objects such as the conical flask, handle them from the base. This makes dropping and smashing the glass less likely to happen.
4. Use a whiteboard; so that any spillages don’t get on to the work benches in the chemistry lab.

Predictions

From my preliminary work and my studies on this topic I can make predictions on what the results in the assessed practical will be.

I predict that as the concentration used doubles the rate of reaction will also double. This is because I am dealing with an experiment which involves changing concentration in an aqueous solution. In this kind of experiment if I double the concentration, this will also double the number of hydrogen ions (H+) in a given volume and therefore you will get twice the number of collisions in a given time. On the other hand if I decrease the concentration there will be less collisions of particles with the calcium carbonate in a given time, this means there will be less effective collisions in a given rate. I think that the concentration and the rate of reaction will be directly proportional to each other, because as the concentration of the hydrochloric acid increases the rate of the reaction will also increase. I should find that the highest concentration used (50cm3 of hydrochloric acid) is five times faster than the lowest concentration used (10cm3 of hydrochloric acid).