Magnesium tarnishes slightly in the air, and fine magnesium ignites upon heating in air and burns with a white flame. Normally magnesium is coated with a layer of oxide (MgO) that protects magnesium from air and water. It is n good conductor of heat and electricity and burns in steam at 1000c to form magnesium oxide and hydrogen (Mg + H2O ==> MgO + H2), it reacts with dilute acids and dissolves in a solution of ammonium chloride and also in solutions of methyl iodide.
I am going to investigate how the concentration of the solution effects how the magnesium and hydroxide react with each other. I am going to time how long it takes for them to react.
The solutions will be measured out in mixtures of:
Variables
In this investigation you could choose to:
- Increase the surface area – there would then be more chance of a successful collision because the particles are spread out.
- Catalyst – This provides a surface for reactants so it brings them together and increases the chance of a successful collision.
- Stir- Stirring moves particles around and moves them faster so it increases the chance of successful collision
- Increase temperature- Increasing the temperature makes particles vibrate faster therefore it increases the chance of a successful collision as particles have more energy.
- Increase concentration- Increasing the concentration means there are more particles in a given volume so there is more chance of them colliding successfully.
Fair Test
To make sure the experiment is a fair test you must make sure that:
- You use the correct amount of solutions
- The same temperature is maintained throughout the experiment
- The beakers are all the same size; if they weren’t then it wouldn’t be a fair test because there would be different surface areas.
- The pieces of magnesium are all the same
- Only one variable is changed
- Make sure you check the meniscus when measuring out the solutions.
- Repeat the experiment to make sure your results are correct.
As the experiment will be taking place in only a School laboratory precise measurements etc might not be exactly the same as equipment isn’t always available. The results should be quite accurate, but not as accurate as they would be if they were done properly in a laboratory with more equipment.
Safety
This experiment inst very dangerous but it does involve acid, so make sure that:
- Safety glasses are worn. This will protect your eyes in case some of the hydrochloric acid is spilt.
- Make sure benches are tucked under desks to avoid trips and falls,
- Hair should be tied back so that it doesn’t get in the way of anything.
- Make sure you stand up for the whole of the experiment.
Equipment
1 Measuring cylinder
2 Beakers
24 cm magnesium (12 x 2cm)
Water
Hydrochloric acid
Stopwatch
Prediction
I predict that the more acid there is in the solution, the quicker the reaction will take place. I think this will happen because there will be more acid particles for the magnesium to react with. The more acidic particles the quicker the magnesium will touch the particles and react. (Mg + 2Hcl → MgCl2 + H2)
I think that there will be no reaction between the magnesium and the solution containing only water, as magnesium doesn’t react with water.
Diagram
Method
- Measure out the first solution into the beakers. Make sure you check the meniscus to make sure you have got the measurements as accurate as possible to ensure it is a fair test.
- Cut 2cm of magnesium and put it into the bottom of an empty beaker. Make sure the beaker is empty and is clean.
- Pour the solution into the beaker with the magnesium in it.
- Start the timer as soon as you pour the solution in.
- Stop the timer when the magnesium starts to react.
- When it has finished reacting clean the beaker and repeat the experiment with the same solution to make sure the experiment is fair.
- Repeat the above for all the solutions
- Record the results in a table.
Results
Conclusion
From the graph I can see that the more acid in the solution the quicker the reaction between the magnesium and the hydrochloric acid happened. This proved my prediction correct. There was no reaction between the magnesium and the solution that only contained water. This was because magnesium doesn’t react with water, but it does react with steam.
When the solution with no water was put with the magnesium I noticed that the reaction took place straight away and gave off lots of bubbles. These bubbles were hydrogen. Putting a burning splint at the top of the beaker could have proved the fact that hydrogen was given off, this would make a popping noise if hydrogen were present. The metal was more reactive than hydrogen so it pushed the hydrogen out, hence the bubbles.
The magnesium proved to be a reactive metal when put with dilute acid.
Evaluation
The results that have I got from the investigation contain only one anomalous results. So apart from the one result this means that they are quite accurate. All the points on the graph are quite close to the line of best fit. I am happy about this; it means that the investigation we did was done correctly.
The result that was anomalous must have been because of human error. We could have measured it out wrong or the stopwatch may have been wrong.
To make the results even more accurate we could have:
When measuring out the solutions more care could have been taken to ensure that the amount was correct. To make them more accurate we could have used graduated pipettes or a burette to make sure that the amount of solution that was put into the petri dishes was right. The meniscus in the beakers of solution should have been checked before the experiment was carried out.
The results are reasonably reliable as there is only one anomalous result. It could have been made more reliable by making the experiment more accurate. This includes making sure all measurements were correct.
You could have also measured how much gas was given off in the reaction between the magnesium and hydrochloric acid. This could have been done with a gas syringe. If I repeated the investigation I would measure the gas as another variable. The investigation could have been improved in lots of ways. Improvements would have made sure that the results were more accurate. Better equipment could have been used, like using pipettes and burettes. The miniscus should have been checked as this could have made a big difference if the measurements were not correct. The experiment could also be repeated again; this then would mean that the average or the best results could be used. If there was more time then the experiment could have been done with more care.
