Investigate what affects the speed of reaction between Hydrochloric Acid (HCl) and Magnesium Metal (Mg).

TEMPERATURE - Increasing the temperature will speed up the rate of reaction.  More kinetic energy means that the particles move faster.  As the particles are moving faster, it increases the probability of collisions happening each second and therefore increasing the reaction time.  The increased energy of the collisions also means that the proportions of collisions that are effective will increase.  The diagram below should improve the understanding of how temperature can affect a chemical reaction.

I got the above information from ‘Collins Science Revision Guide’.

LOW TEMPERATURE                                        HIGH TEMPERATURE

                

SURFACE AREA

Increasing the surface area of a reactant will increase the rate of reaction.

LOW SURFACE AREA                                        HIGH SURFACE AREA

                                 When chopped into pieces.

                                (increasing the surface area)

Only outer particles                                                 Now, more particles are

are expose to be                                                able to react, therefore

able to react.                                                          increasing the rate of

                                                                reaction.

Old surface                        New exposed surface

Imagine one big sweet the size of your hand and 20 little sweets take up the same amount of room on your hand.  You will have more sweet wrappers from the 20 little sweets than the one big sweet.  The 20 little sweet have a higher surface area.

Prediction

I have chosen to investigate how temperature affects the reaction rate between Hydrochloric acid and Magnesium.   My prediction is that the higher the temperature the quicker the reaction will finish.  This is because, when particles are heated, they vibrate quicker and move more rapidly.  When one particle starts to move, it will hit another particle, which will hit another particle, etc…  Therefore, increasing the chance of the particles making a reaction.

A LIST OF APPARATUS/EQUIPMENT – (any type in red is for safety)

• 40ml³ HCl per test, 600ml³ in total.
• 3cm Mg, 45cm in total.
• Beaker.
• Delivery Tube.
• Tub of water.
• Plastic cylinder.
• Cork.
• Thermometer.
• Gauze mat.
• Bunsen Burner.
• Tripod.
• Heatproof mat.
• Matches.
• Timer.
• Sand paper.
• Lab coat.
• Goggles.

DRAWING OF APPARTUS

Step-By-Step Plan

Due to my preliminary work, I notice that 20cm³ of gas (hydrogen) was given off.  Therefore, I will have a better understanding of when the reaction will finish.  Anything in bold type are areas where safety is needed.

1. Clear area, make sure stools and bags are under tables.

2. Set up apparatus.

3. Put on goggles.

4. Heat Hydrochloric Acid (HCl) to specific temperature.

5. Take beaker off heat.

6. Swirl HCl.  This is to try and get an even temperature throughout the beaker  and make the experiment fairer.

7. Add magnesium ribbon to solution.

8. Quickly attach cork to prevent any gas being let out.

9. Start stopwatch as soon as possible.

10. When reaction is finished stop the stopwatch and record the time.

11. Repeat the experiment.

12. After the experiment is finished, clear apparatus.

I will repeat this experiment three times and make an average afterwards.  The more times you repeat an experiment the more accurate it will be at the end.  Due to the amount of time, I will only be able to repeat the experiment three times.  I will be measuring the amount of time it takes for the reaction to take place.  As a result of my preliminary work, I know that I will have to measure the time in seconds as the reaction between HCl and Mg is very quick.

Making an experiment 100% fair is almost impossible, so I will have to try extremely hard to keep many factors the same.  To keep this experiment as fair as possible, I will use the same apparatus.  I will only change one thing in this experiment and that is the temperature.  The only problem I can see with this experiment is making sure that no gas escapes.  Also, the temperature needs to be constant throughout which I will also try my best to do.

Hydrochloride acid is a potentially a very dangerous substance.  On the bottle of HCl, it has an orange symbol on it (as like the one on the right).  This symbol means it can be irritant.  If HCl gets on your skin, it is important to wash the area thorough.  As a result, I will be wearing a lab coat and goggles, to reduce the chances of my skin coming in contact with this substance.  Especially as we are heating the HCl, goggles are very important because when liquids are heated they have the tendency to spit.

(Bars that are circles are anomalous results)

WHAT DO MY RESULTS TELL ME

Generally, the time it takes for the reaction to finish decrease as the temperature increase.  So, the higher the temperature the quicker the rate of reaction is.  This is what was said in my prediction.

Below are various reason on why there maybe anomalous results.

When heating a liquid, some of solution could be boiled off.  Therefore resulting in an uneven amount of HCl.  This leads to the experiment being unfair as the quantities of HCl are not the same with every experiment.  I do not believe that this had a huge effect on the experiment, but I imagine it had some impacted on the final outcome.

When adding the Mg strip to the HCl, the reaction starts immediately.  Because of this, some of the gas (hydrogen), which is produced when the two react, will be lost.  This is because; no matter how hard I try to place the cork over the beaker, inevitably some of the gas will be lost.  This leads on to when to start and stop with timer.  It is hard to add the Mg, place the cork over the beaker, and start the timer.  This is one reason why I did this experiment with a partner to try and reduce the amount of gas lost.  Nevertheless, for me to say ‘start timer’ and my partner to actually start the timer, gas is still lost.  Again a similar problem occurs when stopping the timer.  It is hard to tell, when the reaction has fully stopped.  During the experiment, I had to estimate when the reaction had finished.

Magnesium reacts with the oxygen in the air, just like iron reacts with water and turns into rust.  This layer on the magnesium will make the test unfair if it is not removed.  So, we used sand paper to remove it.  The problem with this is that when you sand down the Magnesium strip, you are also removing Magnesium.  Therefore, the amount of Magnesium is not the same with each strip.  If this experiment was done on a bigger scale, I think it would affect the reaction greatly.  However, as this is not, I do not believe that sanding the Magnesium had a significant affect on the experiment.

If I were to do this experiment again, I would measure how much gas is given off every 10 seconds.  For me to be able to do this, I would have to use a lower concentration of HCl because the reaction is very rapid.  I would also repeat the experiment, to get a more accurate average.