Prediction
I predict that as the concentration of the hydrochloric acid increases, the time taken for the magnesium to disappear decreases. I predict that when the concentration of the hydrochloric acid doubles, the rate of the reaction doubles.
Safety
In order to conduct this experiment safely I will wear goggles all the time while doing the experiment. I will also keep the acid away from my eyes and when pouring it into the measuring cylinder I will put the cylinder on the table and the tour it instead of lifting it into the air and endangering my self and my co-workers.
Bibliography
In order to write up this coursework I had help from the following sources:
Obtaining Evidence
Apparatus
In order to conduct this experiment properly I will be using the following apparatus;
Hydrochloric Acid
Water
10ml test tube
Magnesium Strips
Stop Clock
Beaker
Measuring cylinder
Method
To get the amount of magnesium and the amount of hydrochloric acid to use in the situation, I have to use an excess of acid so that all of the magnesium disappears. An equation for the reaction:
Magnesium + hydrochloric acid >magnesium chloride + hydrogen
Mg (s) + 2HCL (aq)>Mgcl2 (aq) + H2 (g)
Throughout the experiment, I diluted the acid solution using water, as I did this the concentration of the acid decreased. I measured out 10ml of acid and then poured the solution into the beaker with the magnesium strip init and then measured the time taken for the magnesium strip to dissolve, using the stop clock. Next, I diluted the acid by placing 8ml of acid and 2ml of water into the test tube and then poured it into the beaker with the magnesium strip init and measured the time taken for the magnesium strip to dissolve using the stop clock. I then repeated this experiment three more times, with 6ml of acid and 4ml of water, 4ml of acid and 6ml of water and 2ml of acid and 8ml of water. I then repeated this experiment two more times to get a fair test by proving that all my results were accurate, if they were inaccurate I repeated the experiment again, or ignored the wrong result. I recorded the results in a clear table as soon as each experiment was completed, in case I lost them and also to check for possible mistakes in my results. When I did the experiment, I made sure that I started the stop clock at exactly the same time as the acid was poured onto the beaker containing magnesium, to measure the start of the reaction to the finish of the reaction.
The Results Table
The blank results table on the other page is the table that I will use to record the results from my experiment.
The results table that is completed is showing the results from my experiment.
The results on the separate page show the results for the time taken for a magnesium strip to dissolve when it is placed in different concentrations of hydrochloric acid.
From my results table you can see that as the concentration of hydrochloric acid decreased the time taken for the magnesium strip to dissolve increased. This means that my prediction was correct.
Analysing and Considering Evidence
Graph
From this graph you can clearly see that my prediction was correct. The graph shows as strength of the hydrochloric acid increases the rate of the reaction also increases.
This graph shows all my experiments and the tanjets show where the graph stop rising rapidly as they did at the start of the graph. Series one on the graph should be ignored.
Evaluating
Conclusion
I can ensure that if you double the concentration of the acid the reaction rate would also double, this is because the ions are closer together in a concentrated solution. The closer together they are, the more often the ions collide. The more often they collide, the higher the chance of a reaction between the magnesium and the hydrochloric acid. Also there are more particles in the solution which would increase the likelihood that they would hit the magnesium so the reaction rate would increase. The graph gives us a good device to prove that if you double the concentration the rate of reaction doubles.
Evaluation
If I was to repeat this experiment I believe that the results would be a little different. The reason I think this is because; the reaction it self is exothermic. This mean because I used the same test tube through the experiment the temperature of the test tube was varied for every attempt. Next time I would use a water bath, this would control the temperature and wouldn’t affect the experiment. The surface area affected the experiment. As I removed the oxide layer from magnesium, I could only remove certain amounts. Next time to ensure that I have both sides oxide layer free; I might use brand new magnesium. Also as the reaction produced alto of bobbles it lifted the magnesium strip on top of the acid, so it was floating the entire time. This affected the rate of the reaction because the magnesium strip wasn’t entirely in contact with the acid. Also if I was to repeat the entire experiment I would use a burette to measure out the reactants. Also to make sure that I collected all the gas possible I would use a gas syringe.
