Apparatus
- Hydrochloric acid (0.25M, 0.5M, 1M, 1.5M, 2M)
- Magnesium strips (2g each)
- Boiling tube
- Boiling tube rack
- Measuring cylinder
- Gas syringe
- Delivery tube
- Stopwatch
Preliminary Test
I have already carried out a less detailed and accurate investigation on how the concentration of reactants affects rate of reaction.
For this investigation I used hydrochloric acid and calcium carbonate has the reactants and altered the concentration of hydrochloric acid between 1M and 2M. Also I carried out the experiment in a different way that I have in this one. In this investigation I used a measuring cylinder filled with water and then held upside down in a bath of water to measure how much gas was been produced instead of a gas cylinder. Has more gas was produced the water was been displaced from the measuring cylinder and then at the end of the experiment the amount of gas produced could be measured whilst been timed.
The results we got from this investigation were:
In this investigation we found that the higher concentration of hydrochloric acid we used the faster the rate of reaction. This was because there were more hydrochloric acid particles to collide with the calcium carbonate particles for a reaction to take place.
However this method of measuring the amount of gas produced did not work very well, has water could escape from the measuring cylinder causing you think more gas had been produced than there actually was. This is why we wont use this method for this investigation.
Method (Main test)
- Connect opposite end from bung of delivery tube to gas syringe.
- Put boiling tube in boiling tube rack.
- Measure 30ml of 0.25M hydrochloric acid and pour into boiling tube.
- Get someone else to be ready with stopwatch to start timing.
- Release magnesium strip into boiling tube and immediately push the bung end of the delivery tube into the boiling tube whilst telling the person with the stopwatch to begin timing.
- After every 10 seconds record how much gas has been produced in the gas syringe.
- Do this until you reach 50 seconds.
- Repeat steps 2 – 7 for 0.5M, 1M, 1.5M & 2M hydrochloric acid.
- Repeat whole experiment another 2 times and record results in separate tables.
Fair Testing
To make our investigation fair we only changed the independent variable, which was the concentration of the hydrochloric acid, everything else we kept constant. We timed up to 50 seconds because we thought this would give us a good range of results especially for the reactions with higher concentrations of acid. We also improved the reliability of our results by carrying out the investigation 3 times to check for any anomalous results, this also means we will be able to get an average of our results.
Safety
- Goggles – Always wear goggles when handling the hydrochloric acid.
Observations
Most of our results were slightly different each time we repeated the experiment however they were all roughly the same so no anomalous results were found.
Results
Set Of Results 1:
Set Of Results 2:
Set Of Results 3:
Average Set Of Results:
Conclusion
We found out from our average results that when using the high concentration of acid in the reaction, there was a faster rate of reaction. We also found that with the higher concentration of acid the reaction finished earlier than the reactions where a lower concentration of acid was used. Also the greatest rate of reaction was at the start of the reaction. This happened because of the increased amount of hydrochloric acid particles meant that more successful collisions could be carried out in a smaller amount of time. This agrees with my original prediction because my average shows that the higher concentration of acid produced more gas in less time. It also shows that the most gas was produced at the start of the reaction because that’s where the line of best fit is steepest. Where the line of best-fit level out on the graph is where the reaction finished.
Evaluation
I thought our investigation went well and it provided us with a good set of results, which were accurate. Our results were consistent each time we repeated the investigation with the exception of one reaction the second time we repeated it, these anomalous results are highlighted in red in the results table. I’m not sure why those results turned out to be anomalous, there was no apparent reason for it when we carried out the reaction. However after doing an average table and graph not including the anomalous results I think our results are good enough to draw firm conclusions on how the concentration of acid affects the rate of reaction between that and magnesium strip. I don’t think any changes could be made to improve our investigation has it went very well.
