Apparatus:
Gas burette, Conical flask, Stopwatch, Water bath, 2 clamp stands, 2 clamps, delivery tube, 1 gram of small, medium or large marble chips for each experiment, 30cm³ of HCl 2 mole- for each repeat of each acid concentration, Thistle funnel, Measuring cylinder, Electronic balance
Method:
- Set up the apparatus as shown above.
- Find a pair of safety spectacles and put them on before handling the hydrochloric acid.
- In a beaker, pour in some hydrochloric acid (2 molar concentration), roughly about 250ml.
- Take a measuring cylinder, and pour in 25ml of hydrochloric acid ready to be used in the main experiment.
- Measure, on a balance, 1g of large marble chips. This can be accurate up to ±0.05g.
- Put the chips in the conical flask, and place the thistle funnel on top.
- Fill the water bath with water, and then fill the gas burette with water. Carefully place the burette in the water bath, so as not to lose any water from it.
- Place the delivery tube outside the water bath.
- Pour in the 25ml of hydrochloric acid, and after the last drop, start the stopwatch.
- After 30 seconds, connect the delivery tube to the bottom of the gas burette.
- At every 15-second interval, take the reading on the gas burette.
- Repeat this twice more with large marble chips, and then carry out 3 repeats with medium and small sized marble chips.
Results:
Large chips
Average
Medium chips
Average
Small chips
Average
Conclusion
From the graph, we can see that the experiment must have been carried out properly as the lines of best fit of small medium and large chips are arrange in order. As this is what was predicted early, it shows that the results obtained from the experiment are suitable and appropriate.
As readings were taken every 15 seconds, the degree of accuracy may have decreased. However, if recordings were taken every 10 seconds it would make the results more accurate. I have decided to use this time scale in the main experiment.
In addition, from the graph, we can see a few anomalous results that may have occurred as a result of human error. These anomalous results have been highlighted, shown by the circled plots on the graph. Although these anomalies have occurred, it is clear that they have not affected in the overall results in a drastic way, as the lines of best fit are still situated as we predicted.
For the main experiment, I have decided to vary the acid concentration, but only use medium sized marble chips, as this would have the best rate of reaction to compare.