In this experiment I will be using : magnesium ribbon (10 cm strip), hydrochloric acid (1.0M, 0.8M, 0.6M, 0.4M, 0.2M), a flask, a basin, a
delivery tube, water, 100cm3, measuring cylinder, burettes and a timer.
Method
I will use the burettes to get the concentrations of hydrochloric acid accurate. I will put the hydrochloric acid and magnesium ribbon into the flask and start the timer. Every time 10 cm3 of hydrogen gas has been formed I will take down the time, stopping once 100 cm3 of hydrogen has been formed. I will do this twice for all five concentrations of hydrochloric acid in order to get the average; these will then go into tables and graphs to show the results. The tables and graphs will show rates of reaction (volume ÷ time) along with concentrations.
Variables
Controlled – Temperature, surface area of magnesium and volume of hydrochloric acid.
Independent – Concentration of hydrochloric acid
Dependant – Rate of reaction.
The concentration of hydrochloric acid will be altered by the amounts of hydrochloric acid and water in the solution.
Prediction
My prediction, in conjunction with the collision theory is that as the concentration of hydrochloric acid is increased, the rates of reaction will increase too. I think this because the collision theory suggests that the more moving particles there are, the more collisions there will be and there will be a quicker reaction. I think every reaction will be quicker then the previous one and that the difference between the 0.4M experiment and 1.0M experiment will be quite substantial.
Results; tables
Here are the results from my experiment; they show the concentration of the hydrochloric acid, volume of hydrogen produce, and the two experiment times taken and an average worked out from the two times.
0.4 Molar Concentration
0.6 Molar Concentration
0.8 Molar Concentration
- Molar Concentration
Results; graphs
As the graph shows, there is definately a relationship between the molarity of hydrochloric acid and the amount of hydrogen gas produced. The graph shows that the higher the molarity of the acid, the quicker the rate of reaction will be. For example, at 100 seconds in the 0.4M experiment only 29 cm3 of hyrdogen gas was produced, whereas in the 0.6M experiment 65 cm3 is produced. Another example of quicker rates of reaction under higher acid concentrations is the fact that in the 0.4M experiment it takes 448 seconds for 100 cm3 of hydrogen to be produced, whereas in the 1.0M experiment it takes only 47 seconds, a difference of 401 seconds.
I would say that my prediction is pretty much accurate to my results and that the collision theory was correct for my experiment.
Conclusion
I feel that the experiment was quite accurate seeing as my prediction was confirmed as well as the collision theory. My results could have been improved if there were strict conditions with one continuous temperature in the room at the time of the experiment, as it would have eliminated any chance of increasing or decreasing energy in the particles of water, hydrochloric acid or even the magnesium strip.
The concentration and volume of the hydrochloric acid could have also been unreliable, although the use of burettes helped maintain a decent level of accuracy. The ideal method of measuring the volume and concentration of hydrochloric acid is to use industrial machines which are built to measure out chemicals very accurately.
The surface area of the magnesium strip was one of the controlled variables which could have lead to anomalous results. This is because the surface area of the magnesium was not accurately measured; it was only assumed that if we use a 10 cm strip of magnesium there would be no fluctuation in thickness or width of the strip. This could have been improved if magnesium was accurately measured and cut with a cutting instrument, rather than by hand.
Due to the lack of resources presented to us by school, students had to work together to get results which could be used, I have used the same results as a fellow student. My experiment could have been improved if I had completed it myself to my own personal level of detail and accuracy rather than it being done by a group of students where there are more openings for human error.
Saqib Khan
11P
18.10.2003
