Temperature- Increasing the temperature in the reaction will result in the acid particles gaining more energy and therefore moving more quickly and hitting the magnesium more and more increasing the chance of successful collisions.
Surface Area- Increasing the surface area of the magnesium will expose more particles to the acid therefore reducing the time it takes for the reaction to finish as it has a larger surface to attack..
Stirring-Stirring the solution will give the acid particles extra movement energy and increase their speed hitting the magnesium more and more increasing the amount of successful collisions.
Volume Of Acid- Increasing the volume of the acid would increase the amount of particles in the solution therefore increasing the chance of collisions with the magnesium. However this would be limited by the size of the magnesium.
Catalyst- Adding a catalyst to the solution sparks in itself a reaction which would give the particles in the solution more energy and increase their movement rate therefore increasing the chance of collisions between the acid and the magnesium particles.
Variable I Am Going To Change: Concentration of the acid
Variables I Will Keep The Same: Volume of acid
Length of the magnesium
Surface area of the magnesium
Temperature
No catalyst
Same beaker
Same rubber tube
These variables must be kept the same to ensure the test I conduct is a fair one.
What I Am Going To Measure: Time it takes for the reaction to finish
Method: From our preliminary experiments we have decided to use 30cm3 of acid. We know any less than this will result in a temperature rise that may affect our results. First we will set up our apparatus (see diagram). Then we will do the experiment using different concentrations of acid with a range of 0.5 molar to 1.5 molar. We will measure the amount of hydrogen gas produced every 10 seconds to find the rare of reaction. The strip of magnesium we use will be 2cm long each time. We will repeat our readings twice In order to attain an average and hopefully avoid any anomalies that may occur.
Diagram:
Equipment: Conical flask
Hydrochloric acid
Stopwatch
Magnesium strips
Measuring cylinder
Ruler
Empty ice cream tub
Ruber tube
Prediction: I predict that as we increase the concentration of the acid, the time taken for the reaction to finish will decrease. As a result of this the rate of reaction will increase. I believe it will do this because as we increase the concentration of the acid the more acid particles there are to the same volume and less water particles there are, therefore more acid particles will be moving around in the reaction increasing the chance of successful collisions between hydrochloric acid and magnesium particles. Also as the amount of water particles decreases there will be less chance of the acid particles being obstructed by the water particles there fore giving them more chance of colliding with the magnesium.
There was an Anomalous results in the second experiment so they will be discarded (the 0.75’s set) when working out the averages.
Then using the Formulae a = n+n,
2
the table of averages will be made.
Conclusion:
From the graph and my results table i can see that my prediction was proved right .This is due to the fact that i stated that the highest concentration Hydrochloric Acid (1.5M) would have the fastest reaction rate(4.5 cm3 produced in 10 s) whereas the lowest concentration of Hydrochloric Acid (0.5M) would have the slowest reaction rate (1 cm3 produced in 60 s)which were both shown to be correct. However this is not including water which didn’t have any effect on the magnesium whatsoever.This is because in order for any reaction to occur, particles of both substances must first collide.
In a solution with a higher concentration there is a larger amount of particles to react thus allowing for more successful collisions and a higher collision frequency to occur. As reactions rely on successful collisions occuring, a higher collision frequency leads to a faster reaction rate. Furthermore as the number of water particles decreases there is becomes a smaller chance of the acid particles becoming obstructed by the water particles thus giving them more possibilities to collide with the magnesium.
