Concentrations of Acid

Fair test.

To make the experiment a fair test we will have to keep the conditions the same. We have to keep the temperature the same and not stir the acid while it is reacting with the magnesium. Any increase in temperature would cause the particles to move faster and collide more often. If it were stirred it would have the same effect.

We will use the same volume of acid each time and use a 1cm piece of magnesium which has been sanded down to remove the oxide layer.

The only thing that we will change is the concentration of acid. We will do the experiment 3 times with each concentration of acid to get a reliable average.

Safety.

For safety we will wear safety goggles and wash hands after the experiment.

Apparatus.

We will use various concentrations of acid, 1cm pieces of magnesium, water, conical flask, sandpaper, stop clock, safety goggles.

Method.

. Sand down the piece of magnesium to remove the oxide layer and place in conical flask.

2. Add concentration of acid as in table below and start stop clock.

3. When the magnesium has reacted completely stop the stop clock and record time.

4. Do this 3 times for each concentration of acid.

Concentration of acid (mol-dm3)

Amount of acid (ml)

Amount of water (ml)

2

50

0

50

0

0.8

40

0

0.6

30

20

0.4

20

30

0.2

0

40

Results table

Concentration of acid (mol-dm3)

Time taken to react

Time taken to react

2

Time taken to react

3

Average

(mins and secs)

2

0:30:47

0:18:70

0:21:86

0:24

:16:37

:12:92

:15:38

:14

0.8

2:44:02

:37:43

:37:44

:59

0.6

6:47:86

7:25:84

8:46:62

7:39

0.4

7:16:41

6:55:23

7:14:03

7:09

Conclusion

From looking at the results of the experiment I can tell that as the concentration of acid increases the time taken for the magnesium to react decreases.

The 2 mol acid reacted with the magnesium the fastest because it has the most available particles to collide and react with the particles of magnesium. The 0.4 mol acid reacted the slowest because of the high concentration of water present. This meant that there were less particles to collide with the magnesium.

The results which I recorded agree with my original prediction that the stronger the concentration of acid the faster the magnesium reacts.

Evaluation

On the whole the method that we used worked well although we were unable to complete the experiment for the 0.2 mol of acid. The results obtained were generally good. The only odd result was the first result for the 0.8 mol of acid. This was more than a minute longer than the other two results.

The method worked well but to make better use of the time available it would have been beneficial to carry out all three experiments requiring the same concentration of acid at the same time

The results are fairly reliable. The one odd result may have possibly been down to either the size of the magnesium strip being larger than the others or due to it not have been sanded down adequately.

The average of the three results is sufficient to draw a reliable conclusion but the more reactions are carried out the more reliable the results will become.

Chris Longster