Investigating the rate of a reaction - Sample Essay
This is because the rate of reaction shown from the slope is steady. From the graph I can see that the 2 molar acid is blunting more sharply that the 1 molar acid. This indicates that over time, each curve for each molar solution would blunt and plateau if each reaction was allowed to react over a long period of time. In conclusion, from the results I have collected, the graphs I have drawn and the mathematical calculations I have completed I can conclude that as I increase the concentration of the hydrochloric acid, the rate of reaction increases.
This shows that the rate of reaction is affected by concentration – that increased concentration would increase the rate of a reaction. Evaluation During the course of completing the investigation I had faced a few problems. One of the main problems I had faced was that while inserting the bung, pressure built up inside the conical flask which meant that the reading on the gas syringe increased. This meant that while inserting the bung I had to read how much the gas syringe increased by. Due to this I continuously had to minus the reading from my results.
This may mean that I may have got slightly inaccurate results as the reading my not have been perfect – which may have impacted on my final results. I could not find a solution to this problem as every time the bung was inserted the reading on the gas syringe increased. If I was to repeat the experiment I would use a data logging system to record the amount of gas produced. By using a data logging system it would record the amount of gas produced accurately as the system would be connected to the computer which record the results.
Additionally I could have tried to use a beehive case, rubber tubing and a measuring cylinder to measure the gas produced over water. This method may mean that while inserting the bung the gas levels would not increase, which can help in collecting reliable results. In connection to my results, I had three full sets of outliers and one single outlier. I believe that the outliers were due to difficulty in measuring the amount of gas produced. This could have been due to human error in reading the result on the gas reading. Another reason could have been misreading the amount that the gas reading increased by while inserting the bung.
Additionally the use of different sized conical flasks could have also lead to inaccurate results as a bigger size may have trapped more gas and lead to a decreased reading. The outlier results could have been prevented by using a data logging system or a beehive case to measure the gas produced, as describe above. Additionally these outlier results could have been made by not controlling the variable correctly. If I was to repeat the investigation again, there are few aspects I would change which will help in making my results accurate.
Firstly to make the results accurate I would need to press the timer, drop the calcium carbonate chips and insert the bung within a short period of time. This was difficult to do with one pair of hands. This may have caused inaccurate results as the calcium carbonate chips and timer may not have been pressed at the same time, which could have altered my results. Also while inserting the bung some of the carbon dioxide produced may have escaped. This may have caused my results to be slightly inaccurate. Additionally while measuring the calcium carbonate chips, I had only used scales which were to one decimal place.
This means that the variable was not under accurate control, which can cause my results to slightly differ. Also although large sized chips where used, the surface area of the chips was not accurate per investigation. If I was to repeat the experiment I would use either smaller sized or medium sized chips. This would mean that the average surface area per chip would be similar, so therefore the variable would be under control. This would help in decreasing all variance between results, and help me gain accurate results. In addition I the measuring cylinder used was only to a whole number.
This again may mean that the molarity and amounts of solutions may not be accurate, which may have led to inaccurate results. To overcome this problem I should have used a more accurate measuring cylinder, which may be made available to me by the science technicians. Additionally the scale on the gas syringe was only to a whole number. This again may have produced slightly inaccurate results. To overcome this problem I could have used a data logging system. Also while measuring the different solutes while making the different molarity solutions I had measuring the solutions to the bottom of the meniscus.
This was not accurate as human error may have caused slight variance in measuring the solutions. Additionally when making the different molar solutions I had used tap water to decrease the molarity. As the water is not distilled it may not be pure and contain some impurities. This can again make inaccurate solutions of hydrochloric acid. In connection, while stirring the two solutions I used a glass rod. This may not have spread the concentration evenly as some areas of the acid may be more concentrated than others. To overcome this problem I would have used a magnetic stirrer, which would evenly spread the concentration of the solutions.
To work out how accurate my results were I worked out the variance of my results. I had calculated the variance using the formula below: In relation to the variance of my results I can see that most of the variances are below 20% and the average variance is 16. 29%. This show that the results I have collected are reliable. In connection as seen from the graphs, my range bars are relatively small in size. This shows that my results are accurate and that I have made reliable Additionally if I was to complete the experiment again I would complete more sets of results.
This would help me getting a lower variance which means that my results are highly accurate and reliable. I can prove that my range bars are small as the highest range is 4 (2 Molar and 1. 5 Molar), which is relatively low. If I was to complete the investigation again I would complete all the changes above. These changes would help in controlling all variables (surface area and weight of calcium carbonate chips, amount of hydrochloric acid used and temperature), help vary my independent variable (concentration of hydrochloric acid) and help measure my dependant variable (gas produced in time).
I strongly believe if I was to complete the investigation with these changes I would achieve very accurate and reliable results which can help me draw precise conclusions. To draw a strengthened conclusion I would complete the experiment again with different solid and liquid reactants. This would help me prove whether the concentration affects the rate of reaction as other reactants may behave differently. By investigating other reactants, the results would help me prove whether the concentration affects the rate of reaction in other reactants other than calcium carbonate and hydrochloric acid.
An example of another experiment I would conduct is the reaction between magnesium strips and sulphuric acid. Additionally I can continue with the experiment and test the hydrochloric acid with other compounds, or additionally I can conduct a reaction between calcium carbonate and other liquid solutes such as nitric, sulphuric and citric acid.