How does Concentration affect the rate of reaction between Magnesium and Hydrochloric acid?
How does Concentration affect the rate of reaction between Magnesium and Hydrochloric acid?
Secondary resources:
Chemical reactions only occur when reacting particles collide with each other, with sufficient energy to react, this is called the collision theory. The minimum amount of energy required to cause this reaction is called the Activation energy. There are four main factors which affect the rate of reaction. The first factor is:
Temperature of reactants:
When the temperature increases the particles move around faster (because they have more energy). Because the particles are moving faster , they are more likely to collide. When the temperature is low, the particles are slower and they also collide less. The temperature drop lowers the rate of reaction.
Another factor is:
Concentration of the reactants:
Concentration effects the rate of reaction because if there is more of a substance, that means there is more particles. If there is more particles, there as an increase number of collisions and an increased rate of reaction. If there is less of a substance, that means there is less particles, therefore there will be less collisions and an decrease in the rate of reaction.
Another factor is:
The use of a catalyst:
A catalyst is a substance which increases the rate of a chemical reaction, without being used up in the progress. Catalysts are specific, I.e. different reactions need different catalysts. A catalyst lowers the amount of energy needed for a successful collision, so more collisions will be successful and the reaction will be faster . Also it provides a surface for the particles to attach to, therefore increasing the chances in colliding and also increasing the rate of reaction.
The last factor is:
Surface area of solid reactants:
If there is a bigger surface area there as in increase of collisions and also an increase in the rate of reaction, because reactions can only take place at the exposed, outer surface of the solid. If there is a smaller surface area there is less collisions, therefore there is a decrease in the rate of reaction.
Aim:
My aim for carrying out this investigation is to find out whether concentration effects the rate of reaction between Hydrochloric acid and magnesium metal.
Mg+2HCL ---- MgCl +H
Magnesium +hydrochloric acid ---- Magnesium chloride +hydrogen
Pre-test:
I have decided to use the water displacement method to collect the gas. While carrying out my pre-test, I performed experiments with different amounts, times, lengths etc in order to establish the most appropriate quantity.
I have decided to use magnesium granules instead of magnesium strips and magnesium powder because when I experimented with magnesium strip It took way to long for the gas to be collected. When I experimented with magnesium powder the gas was collected to fast. So I decided to use magnesium granules because the time of the gas to be collected. As you can see the results below match my statement.
Magnesium (g)
HCA (cm)
H20 (cm)
Time (s)
0.1g (granules)
20cm
0
2.38
0.1g (strip)
20cm
...
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I have decided to use magnesium granules instead of magnesium strips and magnesium powder because when I experimented with magnesium strip It took way to long for the gas to be collected. When I experimented with magnesium powder the gas was collected to fast. So I decided to use magnesium granules because the time of the gas to be collected. As you can see the results below match my statement.
Magnesium (g)
HCA (cm)
H20 (cm)
Time (s)
0.1g (granules)
20cm
0
2.38
0.1g (strip)
20cm
0
26.70
0.1g (powder)
20cm
0
No time
I have also decided that I will carry out the experiment with the syringe because without the syringe it takes to long to collect the gas, and also it is more accurate to use the syringe because without the syringe some gas will escape.
As you can see my results below match my statement.
Magnesium (g)
HCA (cm)
H20 (cm)
Time (s)
Gas collected (cm)
Factors that were changed
0.1g (granules)
20cm
0cm
2.38 seconds
50cm
With syringe
0.1g (granules))
20cm
0cm
5.67 seconds
30cm
Without syringe
I have also decided that I will collect 30cm of gas rather than 40 or more because for the weaker concentrations to collect the gas it will take to long and for the stronger concentrations too collect the gas it be to fast, so I chose to collect 30cm of gas because it is in between.
As you can see my results below match my statement.
Magnesium (g)
HCA (cm)
H20 (cm)
Time (s)
Gas collected (cm)
Factors that were changed
0.1g (granules)
20cm
0cm
2.38
50cm
With syringe
0.1g (granules)
20cm
0cm
9.21 seconds
30cm
With syringe
I also decided that I will be putting the magnesium in the conical flask first because if you put in hydrochloric acid in first it takes to long for the gas to be collected, so I chose to put the magnesium in first.
As you can see my results below match my statement.
Magnesium (g)
HCA (cm)
H20 (cm)
Time (s)
Gas collected (cm)
Factors that were changed
0.1g (granules)
20cm
0cm
6.36 seconds
30cm
With syringe and magnesium put in first
0.1g (strip)
20cm
0cm
9.81 seconds
30cm
With syringe and acid put in first.
I have decided that I will use 0.1g of magnesium granules because If I use more than 0.1g for the higher concatenations the gas will be collected to fast , and for the weaker concentrations the to collect the gas it will take a long time.
As you can see my results result's below much my statement
Magnesium (g)
HCA (cm)
H20 (cm)
Time (s)
Gas collected (cm)
Factors that were changed
0.1g (granules)
20cm
0cm
6.36 seconds
30cm
With syringe
0.2g (granules)
20cm
0cm
0.11 seconds
30cm
With syringe
I have lastly decided o use the two decimal place stopwatch and weighing scale because my experiment will be more accurate.
Pre-test results table
Magnesium (g)
HCL (cm)
H20 (cm)
Time (s)
Gas collected (cm)
Factors that were changed
0.1g (granules)
20cm
0cm
2.38 seconds
50cm
With syringe
0.1g (strip)
20cm
0cm
26.70 seconds
30cm
With syringe
0.1g (powder)
20cm
0cm
No time
30cm
Without syringe
0.1g (powder)
20cm
0cm
08.28 seconds
30cm
With syringe
0.1g (granules)
20cm
0cm
7.9 seconds
30cm
Magnesium put in first and with syringe
0.2g (granules)
20cm
0cm
0.11 seconds
30cm
With syringe
Method:
I have decided to use the water displacement method to carry out my experiment.
* First of all I collected all the equipment.
* Then I measured 0.1g of magnesium.
* Then I filled up the troph with water, I put the beehive shell in the middle of the troph. Then I got a measuring cylinder filled it up with water, put It upside down in the troph, on top of the beehive shell. Making sure the measuring cylinder is still full of water.
* Then I got a conical flask and put in 0.1g of magnesium granules.
* Then I measured 20cm of hydrochloric acid in a measuring cylinder, before putting in the hydrochloric acid in the conical flask I got my bung and put the syringe in the buns.
* I then put the plastic tubing in the measuring cylinder.
* Then I got my stop watch ready, then I finally put in the hydrochloric acid and then put on the bung.
* I timed how long it took collect 30cm of gas and recorded the time. I repeated the same process 15 times, but I changed the concentration for every experiment.
Apparatus:
* Measuring cylinder
* Beehive shell
* Troth
* Syringe
* Magnesium granules
* Hydrochloric acid
* Water
* Stop watch (2.D.P)
* Weighing scale(2.D.P)
* Plastic tube
Fair test:
To insure that my experiment is carried out fairly I must assure that the mass of magnesium is kept the same throughout the whole experiment. I also must assure that the volume the volume of water in the measuring cylinder is kept the same every time I test a different concentration. I must also assure that if I use a syringe (which is optional) I must use it throughout the whole experiment. I must also assure that I use the same surface area (magnesium granules) throughout the whole experiment. Lastly I must assure that If I am going to put magnesium in first rather than the hydrochloric acid then to do so throughout the whole experiment.
Prediction:
Concentration, temperature, surface area and the use of catalyst effect the rate of reaction. I predict that there is an increase in the concentration of hydrochloric acid, the will be an increase in the rate of reaction, because if there is more of a substance there will be more particles within a given space. So particles will collide more often, leading to more successful collisions so the rate of reaction will increase. I also predict that the lower the concentration of hydrochloric acid, there will be a decrease in the rate of reaction, because if there is less of a substance there will be less particles, therefore there will be fewer collisions, therefore less chances of successful collision so there will be a decrease in the rate of reaction. I also predict that if you double the concentration the rate of reaction will be half of what it originally what it was. I also predict that if you double the concentration, you are doubling the particles, so particles will collide more often, leading to more successful collisions so the rate of reaction will increase, the same pattern will occur if you keep increasing the concentration.
Analysis:
After carrying out the investigation I found out that The concentration that collected 30cm of hydrogen gas the fastest was 1 molar. The concentration that took the longest to collect 30cm of hydrogen gas was 0.4 molar. From the results that I obtained I found a link between concentration and the time taken to collect gas, I found out that The weaker the concentration, the longer it takes to collect 30cm of hydrogen gas and also the rate of reaction decreases. The gas is collected faster for the stronger concentrations because in the stronger concentrations there are more particles than the weaker concentrations, so there is a bigger chance that the particles will collide successfully and increase the rate of reaction. The gas is collected at a slower pace for the weaker concentration because there are less particles, so there a small chance that the particles will collide successfully, therefore the rate of reaction will decrease. The results and graph support the prediction that I made, I predicted that the stronger the concentration, the quicker it takes to collect hydrogen gas and the rate of reaction will also increase, my results prove the first part of my prediction correct so does my graph that I made based on my results. I also predicted that the weaker the concentration the longer it takes to collect hydrogen gas and the rate of reaction will also decrease, my results also prove the last part of my prediction correct so does my graph.
Evaluation:
After carrying out my investigation, I thought my method was very appropriate because I didn't get many anomalous results, based on my background research I thought my results were very accurate. Out of my result table I only obtained one anomalous result, I think I got this result because I forget to turn off the stop watch on time. I could improve my method by weighing the magnesium accurately, which will give me a better result. I also could improve my method by measuring the hydrochloric acid and water accurately, which will give me a better result. I could have also use distilled water or mineral water because these types water are more pure than tap water and would have given a better result. To improve my method I also could have used berates to measure the acid accurately, which would have given me a much better result. The factors that effected my results, that I couldn't control were temperature of water, room temperature and because I carried out my investigation on different days so on the different days the temperature will also be different. I could control temperature by carrying out the experiment on the same day, so the temperature will be the same. I think my results are very reliable I can see a clear pattern that matches my research despite the errors.
Bibliography:
Internet: search engine-www.google.com
Book: What effects the rate of reaction, author-Arthur Kipper
Book: OCR
Science investigation
Shelina Ullah 10G
