What factors affect the rate of reaction of Magnesium and Hydrochloric acid.

Particle A = Magnesium

Particle B = Hydrochloric acid

I predict the rate of reaction of Magnesium and Hydrochloric acid will increase when the Concentration of the acid is increased. This is because the more concentrated the reactants, the greater the number of collisions between particles increase. First of all the particles of the reacting substances must collide with each other, and secondly a fixed amount of energy called activation energy must be reached if the reaction is to take place. If the particles can produce the right amount of energy (i.e. if they collide fast enough and in the right direction) a reaction will take place. The reaction is speeded up if the number of collisions is increased. This also
explains why the greatest rate of reaction is usually as soon as the reactants have been
mixed because they are both at their highest concentrations. As the reaction continues, the concentration of the reacting substances decreases and so does the rate of reaction. So I think when the concentration of the acid is doubled, we double the number of particles, so from this I also think that when the concentration of the acid is doubled the rate of reaction will decrease by half the time than the concentration before.

I predict the rate of reaction of Magnesium and Hydrochloric acid will increase when the surface area of the Magnesium increases. This is because most chemical reactions happen faster when there is more of the reactant to react with. When there is a larger surface area (Magnesium broken down to smaller pieces), there is more of the reactant available, which makes it easier for them to react together. Chemical reactions take place by chance. Particles need to collide with enough velocity so that they react. As the surface area is increased the particles have a bigger surface to react with so more molecules can react at a time. This means that they are colliding more often and there is a bigger chance that the collisions have enough velocity to cause a reaction. Since there are more collisions the chemical reaction takes place faster. From these notes I think when the surface area is doubled the rate of reaction decreases by half the time than the surface area before.

General formula:

Magnesium (s) + Hydrochloric acid (l)            Magnesium Chloride (l) + Hydrogen (g)  

Mg (s) + 2HCl (l)             MgCl2 (l) + H2 (g)

Method 1 (Temperature): 

• Add 25 ml of (2 molar) Hydrochloric acid in to a conical flask
• Heat it by putting it in a water bath
• When the acid reaches 60ºC, add a strip of (5 centimetre long) Magnesium to the acid
• Use a stop watch to time how long it will take before the Magnesium strip dissolves

I used the same method for 40ºC and 27ºC (room temperature).

Method 2 (Concentration of acid):

• Add 25ml of (0.5 molar) Hydrochloric acid in to a conical flask
• Add a strip of (5 centimetre long) Magnesium to the acid
• Use a stop watch to time how long it will it take before the magnesium strip dissolves

I used the same method of 1 molar and 2 molar of Hydrochloric acid.

Method 3 (Surface area):

• Add 25ml of (1 molar) Hydrochloric acid in to a conical flask
• Add a strip of (1.25 centimetre long * 4) of Magnesium to the acid
• Using a stop watch time how long it will take before the Magnesium strip dissolves

I used the same method for 2.50 centimetre long * 2 and 5 centimetre long magnesium strips.

I did all my investigation three times to make my result accurate. To make my experiment fair I used the same amount acid for all the experiment and used the correct amount of Magnesium for all the experiment. I cleaned the conical flask after every experiment to make sure none of the solution from the previous experiment was still in the flask. I made sure that none of the solutions was stirred because this can also increase the rate of reaction.

Results:

This table shows the result of the ‘Temperature’ experiment.

Average:

27ºC = 40 sec

40ºC = 29 sec

60ºC = 21 sec

This table shows the ‘Concentration of acid’ experiment.

Average:

0.5 molar = 15:16 sec

1 molar = 3:14 sec

2 molar = 0.25 sec

This table shows the ‘Surface area’ experiment.

Average:

5cm = 3:14 sec

2.50 cm * 2 = 2:41 sec

1.25 cm * ³ = 2:56 sec

Conclusion:

From my results I can say that when the temperature is raised, surface area is increased and concentration of the acid is increased that the rate of reaction speeds up.

My ‘Temperature’ results clearly points out that when the temperature is raised the rates of reaction speeds up very quickly, as my result shows that nearly 10 seconds were taken away every time the temperature was raised. But in my hypothesis I said that the when the temperature is doubled it would half the time then the temperature before but it did not happen. This shows that when the temperature is doubled, the time don’t take half the time then the temperature before.

 My ‘Concentration of acid’ result shows us that when concentration of the acid is increased the rate of reaction increases rapidly. It took an average time of 15:16 sec for the Magnesium to dissolve when the concentration was 0.5 molar, whereas it only took 3:14 sec when using 1 molar and 0:25 sec when using 2 molar. Again in my Hypothesis I said that it would take half the time when you double the concentration then the concentration before but it took much more time than I thought it would. My results don’t show a pattern but it shows that there is a dramatic change when the concentration of the acid is increased.

My ‘Surface area’ result shows that there is a slight difference when there is an increase with the surface area. Although I think that this is inconclusive because my 2.50 centimetre long * 2 strip takes less time than the 1.25 centimetre long * 4 strip.