Rates of Reaction Practial

Apparatus:

• Two beakers (400ml)
• Large Calcium Carbonate Chips (5g)
• Small Calcium Carbonate Chips (5g)
• Calcium Carbonate Powder (5g)
• Hydrochloric Acid 1M (100ml)
• Spatula
• Accurate Scale
• Stopwatch

Method:

1. Collect all of the equipment and measure 5g of each size of surface area of Calcium Carbonate with a spatula.
2. Collect 100 ml of Hydrochloric Acid into one of the 400ml beakers.
3. Place the other beaker on the scale and then set the scale measure to zero. Pour the 100ml of HCl into the beaker on the scale.
4. Hold a stopwatch in one hand, and place the large CaCO3 chips into the beaker containing HCl. Start the stopwatch as soon as the chips contact with the surface of the acid.
5. Record the loss of mass on the scale every 10 seconds for 1 minute and 30 seconds.
6. Repeat the same steps for small calcium carbonate chips and calcium carbonate powder.

Results Table:

The following table displays the loss of mass in solution every 10 seconds:

Results Graph:

Conclusion:

  From observing my results I have found out that powder has the quickest rate of reaction, then comes small marble chips and lastly large marble chips have the slowest rate. This is because when the size of particles is reduced it increases the surface area available for collisions to occur.

When the chip is larger the acid particles can only collide with the edge of the chip. If the chip is cut into several smaller pieces, the acid particles (in the second diagram) can now reach the centre part of the original larger chip. This is why the powder had the quickest rate of reaction. In conclusion my prediction was right. I predicted that the smaller the chips the faster the rate.

Evaluation:

  When I started the experiment my original plan was to react zinc with hydrochloric acid. After two attempts I found out that the mass did not drop after a long while because it produced hydrogen gas, which was a very light gas. So instead I used Calcium carbonate so that carbon dioxide is produced therefore it is easier to measure the mass drop. This is because while carbon dioxide is a lot denser and 22 times heavier than hydrogen gas while having the same volume at R.T.P (room temperature and pressure), therefore the mass drops 22 times faster than hydrogen. During my test for large marble chips I had an anomalous result. At 80 seconds the mass of my solution increased and then decreased again. I figured that this was because of a sudden technical problem with the scale, or something happened at the same time causing the sensitive scale to respond to it therefore I should have repeated the measurement to get an accurate result. Another big issue was that I did not know the actual surface areas, only the relative quantities. This means that I could only compare and assume that the powder had more surface area than the large calcium carbonate chips. I then figured out a way to solve this problem, which is to purchase calcium carbonate chips cut into cube form in different sizes. This way I would be able to measure and calculate the surface area of each size of calcium carbonate cube therefore I would actually know the surface area. This way not only would I have more surface areas to confirm the trend, my results would be much more accurate and clear.

If I could do this experiment again I would repeat my method but record every 30 seconds instead so that the change is more visible, and record until 3 minutes so that the calcium carbonate would dissolve more thoroughly. I would also repeat it several times to make sure my results are accurate and reliable and that my prediction was right and experiment on more surface areas to confirm the trend.