The aim of this experiment is to find out what effect the amount of magnesium has upon the amount of hydrogen gas produced.

• I will be leaving the reaction for 2 minutes each time. This is because, if the reaction was left for a long time, there would be more time for the molecules to move around, displacing more hydrogen, the same as if there was less time, there would be less time for the molecules to move around displacing less hydrogen gas.

• I will measure out the magnesium and cutting it in 1cm intervals, i.e. 1cm, 2cm, 3cm, 4cm, 5cm and 6cm. This is so that it is easier to see if there is a pattern in the amount of gas displaced because there is an equal pattern to the amount of magnesium used, in other words, I will be able to see if the amount of gas produced is proportional to thee and of magnesium used.

• I will be using the same concentration of acid so that there is the same amount of molecules for each reaction. This is because if there was a higher concentration of acid there would be more molecules for the magnesium to crash into, releasing more hydrogen the same as if there is a less concentrated acid there would be less molecules for the magnesium to crash into, releasing less hydrogen gas.

Apparatus

The apparatus I will be using is:

• Ruler
• Conical flask
• Bowl
• Retort stand
• Delivery tube
• Measuring cylinder (250ml)
• Hydrochloric acid (1.5molar)
• Stopwatch
• Magnesium ribbon
• Bung (with hole through the centre)
• Water
• Safety specs

The apparatus will be set up like this:

Method

• The first thing is to put on the safety specs.
• Fill the conical flask with 100ml, using the scale of the side, of 1.5molar hydrochloric acid.
• Fill the bowl with water.
•  Fill the 250ml measuring cylinder with water and turn it upside down in the bowl.
• Use the retort stand to hold the measuring cylinder upright in the bowl.
• Put the delivery tube into the bottom (the open end which is under the water) of the measuring cylinder.
• Use a ruler to measure 1cm of magnesium ribbon and cut it with a pair of scissors.
• Put the magnesium into the acid in the conical flask, start the stopwatch and put the bung into the top of the conical flask.
• When 2 minutes is up, record in the table the amount of gas produced, by reading off of the ml scale on the side of the measuring cylinder.
• Empty out the acid and magnesium.
• Refill the conical flask with 100ml of acid by using the scale on the side.
• Measure and cut 2cm of magnesium ribbon.
• Refill the measuring cylinder and out in into the bowl.
• Put the delivery tube into the measuring cylinder.
• Put the magnesium into the acid in the conical flask, start the stopwatch and put the bung into the top of the conical flask.
• When 2 minutes is up, record in the table the amount of gas produced, by reading off of the ml scale on the side of the measuring cylinder.
• Repeat the reaction with 3cm, 4cm, 5cm and 6cm of magnesium ribbon.
• When I have done this I will repeat all of it again so that I get 2 sets of results.

To make the experiment as safe as possible I will be wearing safety goggles and I will clean the desk if any acid is spilt.

Results table

Graph for average results

Analysis

As you can see from my graph the amount of hydrogen produced almost proportional to the amount of magnesium used. In other words the more magnesium molecules, the more there is to react with the chlorine molecules displacing the hydrogen as gas

Mg + HCl2 → MgCl2 + H2

   Magnesium + Hydrochloric acid → Magnesium Chloride + Hydrogen

My prediction is entirely correct because I said that the more magnesium used the more hydrogen gas will be produced. My results show this in that when I used 1cm of magnesium ribbon, 13ml of hydrogen gas was displaced and when I used 6cm of magnesium ribbon, 72ml of hydrogen gas was displaced.

Evaluation

I found my results fairly reliable because they form a linear line on my graph. There is one anomaly on my graph, being the 6cm reading, as it is much further away from the line of best fit. I think it is there because I had to dilute 2molar acid down to 1.5molar acid. I did this by adding 75ml of 2molar acid with 25ml of water. When I did this I couldn’t measure the amounts exactly and I think that is why that is the anomaly. The rest of my results are otherwise reliable. If I did this experiment again I would use a gas cylinder/syringe so that I could get the most accurate reading possible. I would also weigh the mass of the magnesium instead of measuring the length because the magnesium is not the same thickness all of the way down, In turn making more/less molecules to react with the chlorine. The bung could have been fitted into the top of the conical flask tighter and the delivery tube could have had a more airtight seal with the bung. If I had to do the experiment again I would change the surface area of the magnesium to see if this had and effect on the amount of hydrogen gas produced, i.e. ground up magnesium (more surface area) and a lump of magnesium (less surface area).