Rates of Reaction Investigation

St. Patrick’s Comprehensive

Aim

To find what variables affect the rate of the reaction between magnesium and sulphuric acid.

Variables

The variables for this investigation are:

§ Concentration of acid

§ Size of magnesium

§ Temperature of acid

§ Amount Of Acid

Prediction

I think that the higher the temperature of the acid, the faster the reaction. I think this because an increase in temperature makes particles move faster, thus making them collide more often, and I also think the smaller the amount of magnesium, the faster it will react. For the concentration experiment I think that the more water in the concentration the slower the reaction.

To make the test fair

To make the test fair I have decide to use the same amount of sulphuric acid (20ml) each time and the same amount of magnesium (0.01g).

Diagram

Method

I collected all the necessary apparatus, then I then poured 20 ml of acid into a conical flask and added a folded strip of magnesium (weighing 0.01g). Using a stop watch I then timed how long the reaction took. As soon as all movement in the flask ceased. I stopped the stop watch and recorded the time taken in a table. I poured 20 ml of acid again into a beaker and using a Bunsen burner heated it until the temperature was 25 C on the thermometer. When it reached this temperature I took the beaker off the Bunsen burner and put it on the haet proof mat. I then added a strip of magnesium (once again weighing 0.01g) and using a stop watch timed how long the reaction lasted for. The time taken was then recorded in the table. This test was performed again the acid was heated to 30 C, 40 C, 50 C, 60 C. and 70 C. All my results can be observed in the table below.

Temperature

Time Of Reaction

25 C (Room Temp)

55 sec

30 C

44 sec

40 C

42 sec

50 C

40 sec

60 C

38 sec

70 C

36 sec

I then performed the same test a further 2 times, to have sufficient information so that I could work out my average.

Temperature

Time Of Reaction

25 C (Room Temp)

54 sec

30 C

49 sec

40 C

38 sec

50 C

37 sec

60 C

35 sec

70 C

31 sec

Temperature

Time Of Reaction

25 C (Room Temp)

45 sec

30 C

40 sec

40 C

37 sec

50 C

35 sec

60 C

32 sec

70 C

30 sec

My averages for the experiment were;

Temperature

Time Of Reaction

25 C (Room Temp)

51 sec

30 C

44 sec

40 C

39 sec

50 C

37 sec

60 C

35 sec

70 C

32 sec

Secondary Sources

I performed a second test to see if to see if the rate of reaction was affected by the concentration of the acid, so I added 5 ml of water to 15ml of acid, added 0.1g of magnesium strip and timed the reaction, I did this three times, then moved on to 10 ml of acid and 10 ml of water, performed that three times and then did 15 ml of water and 5 ml of acid, performed that three times and worked out my average.

Amount Of Acid

Amount Of Water

Time Taken To React (1)

Time Taken To React (2)

Time Taken To React (3)

Average Time

15 ml

5 ml

69 sec

65 sec

70 sec

68 sec

10 ml

10 ml

170 sec

160 sec

162 sec

164 sec

5 ml

15 ml

521 sec

501 sec

510 sec

510 sec

Conclusion

I have found as can be seen in the graph that as the temperature increased the reaction time decreases. This is because at higher temperatures, particles are moving around faster. They therefore collide more frequently and with more energy.

When the magnesium is in smaller pieces more surface area is exposed, this means acid particles collide more frequently with particles on the magnesium and cause it to react quicker . I also found that in the reaction between magnesium and sulphuric acid hydrogen is given off. I found this from doing a gas test with a lit spill. When the spill was placed in the test tube were I had collected the gas it made a popping noise, thus telling me that the gas was hydrogen. The equation for the reaction between the magnesium and sulphuric acid can be seen below;

Magnesium + Sulphuric Acid ŕ Magnesium Sulphate + Hydrogen

Mg + H SO ŕ Mg SO + H

Evaluation

I found my results for the magnesium strips followed some sort of pattern, but I noticed that on some tests there is considerable differences in reaction time . The only