1 mode of any gas at room temperature has a volume 24000cm3
The volume of 2 test tubes is about 100cm3
If 1 mole Hydrogen is 24000cm3, then 2 test tubes (100cm3) is about
100cm3/24000 cm3=1/240 mole
From 2HCL + Mg ------ MgCL2 + H2,
1/240 mole Hydrogen =1/240 mole Mg = 2/240 mole HCL
mass Mg =1/240 *24=0.1 g
2 mol/dm2 =2 mole in 1000 cm3
Minimum volume HCL: (2/240)/(2/1000)=4.2 cm3
As the calculation show above, in the experiment, we need the minimum volume HCL 4.2 cm3 and 0.1 g magnesium.
PRELIMINARY EXPERIMENT:
I am going to do the preliminary experiments to see whether it works or not.
During the experiment, I am going to use 25ml3 HCL and 24g Mg. I choose the amount of reactant much greater as in case they will use up, so I can’t collect enough Hydrogen.
The preliminary experiment is very important, as we could make sure that the reaction is not too quick and the cylinder is not big enough to fill up all the Hydrogen gas. Also make sure that the reaction is not too slow and give us a small range of data.
In this experiment, I am going to carry out to find the mass of Mg to use and this experiment is also uses to test the range of concentration to use in the experiment. These experiments were important to carry out because we could make sure the reaction did not fill up the boiling tube too quickly which gibe a inaccurate result. This could also make sure the reaction did not take place too slowly to give us a small range of result.
I am going to use the acid with the concentration of 2mole/dm3. I will use magnesium with the mass from. In order to collect the hydrogen, I will use the boiling tube which full with water and measure how long it takes a boiling tube to be filled with Hydrogen. We react both of the reagents in a conical flask and measured the mass of the Mg on an electronic balance to get a fairly accurate reading.
My results are shown underneath:
From this we decide the best mass to use was 0.25g this was because this reaction took place at a reasonable rate because it was fast enough to get a wide range of results, but anything faster would make the experiment hard to record as the boiling tube would be filled too quickly.
ACCURACY:
In this investigation, I will vary the concentration of HCL by adding the same amount of water instead of HCL. Because this give me enough data 10 points for me to draw an accurate graph.
I predict that the average time for the HCL to fill the boiling tube is 3 min; this gave me time to repeat the experiment twice. So I would have more accurate average. The time will be measured to the nearest millisecond.
I would measure the volume to the nearest cm3
SAFETY:
I will make sure our method is safe by wearing safety goggles and follow the safety procedures carefully.
I will follow the lab safety roles:
- Put all bags under the table;
- Never run in the lab;
- Never sit down when doing the experiment
PREDICTION:
I predict that:
- The higher the concentration of the Hydrochloric Acid, the quicker the reaction, so the more Hydrogen can be collect. As the collision theory showed above, the higher concentration means that there are more particles in the acid, as it reacts with Magnesium, they will collide more often with the Magnesium. This will increase the rate of reaction, so more hydrogen can be collect.
- The rate of reaction will decrease as the experiment longer the experiment progresses. This is because as the Hydrochloric Acid react with the Magnesium, the number of Hydrochloric Acid will decrease to form water Magnesium Chloride and hydrogen. This will decrease the rate of reaction because of decrease of concentration. As the result, the graph shows the relationship between the increasing of Hydrogen and the time will be a curve, which the reaction rate slows down as the time increases.
- The increase in concentration should be directly proportional to the increase of reaction rate at a given time. For instance, the volume of the hydrogen will double when the concentration of the acid double. This is because as far as I double the concentration of the acid, there is double number of Hydrochloric acid particle in a given volume, so the chance of the collision of the acid particle with the magnesium will double.
APPARATUS:
2 boiling tubes: use to collect the hydrogen gas
1 Clamp: use to hold the boiling tube
1 Delivery tube: use to connect the boiling tube and the conical flask to deliver the hydrogen gas
1 *250cm conical flask: use to hold the reactants
1 Stopwatch: use to measure the time it takes to fill the boiling tube
1 Measure cylinder: use to measure the volume of HCL
1 container: use to put the boiling which filled with water upside down
Hydrochloric acid
Magnesium
METHOD:
- Fill the container and the boiling tube with water; put the boiling tube upside down into the container so the boiling still fills with water. This is because some of the water was displaced by the Hydrogen gas. Clamped the boiling tube in place. Make sure there is no bubble in the boiling tube.
-
Measure 25ml3 HCL acid by using measure cylinder.
- Measure 24g of Mg by electronic balance to one decimal place and put it into the conical flask.
- Pour the HCL into the conical flask.
- Put the delivery tube under the boiling tube and upon the conical flask immediately after you pour the HCL, so the gas from the experiment could displace the water.
- Start the stop- watch as far as you see the first bubble comes out from the delivery tube.
- Stop the stopwatch when the boiling tube has been filled.
While doing this experiment, I have to work carefully to avoid accidents and follow the safety procedures.
The graph shows below describe how the experiment set up:
EVIDENCE:
I followed the safety procedures and the method I mention above to carry the experiment.
The measurements I feel were fairly accurate as the results were what was expected. These were only one anomalous result. I repeated the experiment twice so we could find averages and get more accurate and reliable results. The results were measured to nearest centimetre cubed because this was the maximum accuracy of the cylinders. The results show the results we got for each experiment.
ANALYSIS AND CONCLUSION:
I am going to do the calculation of the results form the same concentration were added together and divided by 2 (the number of experiments).
The mean = (test one result +test two result)/2
I am also going to calculate the rate of reaction by using 1 divide by the average time take
The results show below:
The graph in the next page shows the relationship between the rate of reaction and the concentration:
From these results and the graph, we can conclude that by increasing the concentration of hydrochloric acid the reaction rate in increased. It shows that the highest concentration had the highest reaction rate and only needed 3.30s to fill the tube, whereas the lowest concentration needed 391.16s to fill the tube.
This is the same as my prediction.
The fact that the reaction rate was highest at the highest concentrations shows that the higher the concentration the more particles that are present per set volume which shows increases the rate of reaction.
EVALUATION:
The results that the experiments showed was supported my prediction, as it shows that increasing the concentration of hydrochloric acid the reaction rate in increased. The change is bigger when the concentration is higher, which means my experiment is successful.
From my results table and graph, I can see that my results that I collected are quite reliable and accurate. I know this because my results table shows a few, individual anomalous results; the anomalous result when the concentration of the HCL is 1.2 mol. The anomalous result shows the time the reaction takes is slightly longer than I predicted. All the other points are extremely close to the line indicating that my results are accurate.
In the Analysis and the graph I have shown one main anomalous points, this means that there must have been a slight error in my experiment. Although the graph is overall accurate and the results precise it is easy to see, the anomalous averages plotted may because the mass of the magnesium being measured slightly inaccurately. Another possibility is because the surface of the magnesium may be smaller than the others. The graph shows that my results are reliable as there are only one main anomalous points, (which are easily accounted for) to improve the reliability of my results, I could do more repeats in doing this my average would be more reliable.
The measurements of the volume of the water and HCL were accurate to about, and the measurements of the time were accurate to about millisecond.
The difficulty in this experiment is that, when turning the cylinder upside down little volume of water was lost, this caused the time we get is smaller than it suppose to be. To solve this problem we, could use a gas syringe.
The experiments were fair tests to a certain point, but there was a certain error because the results recorded were only to the nearest cm3. And the values of the controlled variables—the mass of the Mg and the volume of the HCL were not exact amounts so this may have been slightly differently each time which would have affected slightly the reliability of the results. We also can not keep the room temperature and the boiling tube is dry each time, this affect the reliable of the results.
To improve the experiments and the make the results more reliable, I would try my best to keep all the confounding variable the same. I would also use top quality equipment. I would also repeat the experiment by using the same concentration more times to get more reliable reading.
If I am going to do a further investigation, I will find out whether the concentration keeps increasing the rate of reaction of this only happens to a certain extent. This could be found out by extending the range of concentrations reacted. However, theses reactions can be very dangerous as the concentration of the acid is too high.
