Prediction
I predict that as I increase the concentration of the hydrochloric acid (2M), the rate of reaction will increase; this is because when the acid in a solution is more concentrated there are more acid particles in it. Thus meaning that there is more chance of a successful collision occurring between the magnesium atoms and acid particles. The more successful collisions there are between the magnesium atoms and the acid particles, the faster the reaction.
Equipment
- Goggles
- two measuring cylinders
- six boiling tubes
- test tube rack
- stopwatch
- six, 1cm pieces of magnesium
- water
- a bottle of 2M hydrochloric acid
Method
Firstly I measured out 30ml of 2M hydrochloric acid in a measuring cylinder and poured it into a boiling tube, then I placed the boiling tube in the test tube rack and got a piece of 1cm magnesium strip on standby. Then I got the stopwatch ready and placed the piece of magnesium into the boiling tube with the acid in, as soon as the magnesium strip made contact with the acid I started the stopwatch going. I stopped the stopwatch when the magnesium strip had completely disappeared and recorded my results. I then repeated the experiment using 25ml of 2M hydrochloric acid but also added 5ml of water into the acid using the other measuring cylinder before adding the magnesium. I then repeated the experiment using different concentrations of acid and water but still kept the same volume of liquid. The concentrations will be as follows :- 30mls of acid, 25mls of acid to 5mls of water, 20mls of acid to 10mls of water, 15mls of acid to 15mls of water, 10mls of acid to 20mls of water and finally 5mls of acid to 25mls of water.
Diagrams
Measuring Cylinder boiling tube with acid and water in
Results
Table
1st try
Volume of acid Volume of water Time taken for 1cm strips of magnesium to be dissolved
30ml 0ml 26.47 seconds
25ml 5ml 2 minutes 5.78 seconds
20ml 10ml 1 minute 40.75 seconds
15ml 15ml 2 minutes 8.28 seconds
10ml 20ml 6 minutes 57.21 seconds
5ml 25ml 10 minutes 16.33 seconds
2nd try
Volume of acid Volume of water Time taken for 1cm strips of magnesium to be dissolved
30ml 0ml 29.51 seconds
25ml 5ml 2 minutes 20.01 seconds
20ml 10ml 1 minute 30.73 seconds
15ml 15ml 2 minutes 12.78 seconds
10ml 20ml 6 minutes 59.01 seconds
5ml 25ml 10 minutes 25.13 seconds
Graph
See graph paper
Conclusion
I have plotted my results onto a bar graph and plotted a line of best fit it. It has become apparent that I have an anomalous result, on both tries using 20mls of acid the time taken for the magnesium to dissolve was shorter instead of being longer. After completing my experiment I can say that my prediction was correct, this is because in general my results showed that the higher the concentration of acid to water the quicker a 1cm piece of magnesium was destroyed, this is because as I have previously said, the more acid atoms there are in the water (when the acid is more concentrated) the more chance there is of the acid particles colliding with and destroying the magnesium atoms. Thus I have concluded that the more concentrated the acid in a solution is, the speedier the reaction.
The reaction and products made by the reaction can be expressed as the equation:-
Magnesium+ hydrochloric acid magnesium chloride+ hydrogen
Mg(s) + 2HCL (aq) MgCl (aq) + H (g)
Evaluation
In general I think that my experiment went well, and that my conclusion was well proven and founded. Although the experiment went well it could have gone better and things could have gone wrong. For example measuring errors may have occurred unintentionally and when observing the magnesium dissolving I could have slightly mistimed the stopping of my stopwatch and obviously under stricter lab conditions the results would have been more accurate and better. I believe that my results were accurate apart from the one anomalous result I obtained and that if I repeated the experiment for a third times my results would be the same.
