As you can see, as you increase the concentration, there are more particles to collide with each other. This indicates that the rate of reaction will increase as the concentration increases.
Once I have my results I am going to find the averages and place these points on a graph. I will then draw a line of best fit, whether it is a curve or a straight line. Then, using the line of best fit I will calculate the rate of reaction by, if the line of best fit is a curve, I will draw a tangent on my line of best fit and then draw a right-angled triangle from the tangent.
Using the triangle I will work out the tangent of the slope by doing the following:
This will then tell me how fast the gas was produced for each concentration. This will make comparing the rates of reaction clearer.
Fair Testing
I will make my experiment a fair test by doing the following things:
- I will keep the Hydrochloric acid at a constant temperature- This is not possible for me to control as the room temperature will determine the temperature of the acid, and I cannot control this. The temperature of the classroom changed, throughout the experiment, between 20°C and 23°C.
- I will use the same amount of Calcium Carbonate- I will do this by weighing each piece and making sure each piece weighs 1g.
- I will use the same amount of acid- I will do this by measuring out 50ml of the acid each time.
- I will time the same amount of time for each go- I will do this by using an electronic timer.
- I will keep the surface area of the Calcium Carbonate the same- I will try and do this by using pieces that are of the same shape. However, this may not be possible.
Equipment
The equipment I will require to complete the experiment will be:
- A delivery tube
- 15 x 1g of marble chips (15g)
- 3 x 50ml of 0.5M Hydrochloric acid (150ml)
- 3 x 50ml of 1M Hydrochloric acid (150ml)
- 3 x 50ml of 1.5M Hydrochloric acid (150ml)
- 3 x 50ml of 2M Hydrochloric acid (150ml)
- 3 x 50ml of 2.5M Hydrochloric acid (150ml)
- A thermometer to 1°C accuracy
- Goggles
- Timer
- Scales to 0.1g
- A 100ml conical flask
- A 100ml beaker
- A 25ml measuring cylinder
Method
- Measure out 50ml of Hydrochloric acid into a 100ml conical flask.
- Fill up a 25ml beaker and a 100ml measuring cylinder with water.
- Put the measuring cylinder, upside down, into the beaker ensuring no water escapes from the measuring cylinder. This will ensure any gas going into the cylinder will replace the water and an accurate reading can be taken.
- Put the delivery tube under the measuring cylinder in the beaker.
- Add 1g of Calcium Carbonate marble chips to the Hydrochloric acid in the conical flask, and immediately afterwards put the bung from the delivery tube into the conical flask, and start the timer, to trap any gas given off.
- Time for one minute, and record the volume of gas collected in the measuring cylinder every 10 seconds. Once the one minute mark is reached, remove the bung from the conical flask and then record how much gas was collected in the measuring cylinder.
- Repeat this twice with the same concentration of Hydrochloric acid.
- Repeat this whole experiment with another 4 different concentrations of Hydrochloric acid.
Diagram of Equipment
Safety
To make sure my experiment is safe, I will wear goggles to protect my eyes from the Hydrochloric acid and keep all bags and stools under tables to prevent me from tripping and falling with acid. I will mop up any spills straight away to stop me from slipping over, which could prove dangerous if I was carrying acid.
Preliminary Findings
Primarily, I had decided to dissolve 3g of Calcium Carbonate marble chips in 50ml of hydrochloric acid for 5 minutes. However, all of the marble chips had dissolved before the 5 minutes. As a result of this I decided to time for a shorter amount of time. I decided to time for 1 minute. However, the marble chips still dissolved too fast so I decided to, instead of shortening the length of time, use a smaller amount of marble chips. Instead of using 3g I chose to use 1g. Inevitably the experiment worked. The marble chips did not dissolve too fast or too slowly. This is evident from the following results table.
Preliminary Results
Results
Analysis
From looking at my results and graph, it is evident that the higher the acid concentration the faster the rate of reaction is. It is also evident that the biggest changes in the rate of reaction happened mainly in the last 30 seconds.
From my graph I can see that when I used the 2.5M concentration of Hydrochloric acid, the rate of reaction was fairly constant throughout. It increases at a speed of 0.4cm³/s.
My graph also shows that when I used the 2M concentration of Hydrochloric acid, the rate of reaction increased again at a fairly constant rate of 0.18cm³/s, which is nearly half as much as what the 2.5M concentration produced.
When I used the 1.5M concentration of Hydrochloric acid, the reaction started off quite slowly, however, after 20 seconds had passed, the substance had started producing nearly 2cm³of gas every ten seconds. From the calculations on my graph I can see that the 1.5M concentration produced 0.13cm³/s. This is 0.05cm³/s less than what the 2.0M concentration produced.
When I used the 1.0M concentration, it produced 0.11cm³/s of gas. This is nearly half as much as the 2.0M concentration produced. This proves that my prediction was correct and that if you double the concentration the volume of gas produced will be doubled. However, the graph shows that when the 0.5M concentration of Hydrochloric acid was used, the rate of reaction happened very slowly and only produced 0.01cm³/s of gas. This does not follow the theory that if you double the concentration the volume of gas produced will be doubled. This could mean one of two things: either the results taken for the 0.5M concentration were inaccurate or the theory is incorrect.
Evaluation
The experiment went well because of the preliminary testing. This helped determine the best way to get accurate and reliable results. The results were as I had expected. However, all of them did not follow the pattern I had expected: that if the concentration is doubled the volume of gas produced would be doubled.
There were two anomalies amongst my results. When using the 1.5M concentration of Hydrochloric acid, after ten seconds the volume of gas produced was 0cm³. This did not fit on the line of best fit for the 1.5M concentration, and to have fit on the line of best fit it would have had to have produced approximately 1.3cm³ of gas. This anomaly could have happened because the temperature in the room could have changed and not stayed at a constant temperature. Also, the surface area may have affected how the experiment substance reacted. The second anomaly was when I used the 2.0M concentration of Hydrochloric acid. After 60 seconds, the volume of gas produced was 14.3cm³. This appeared to be too high to fit on the line of best fit. The reason for this anomaly will be the same reasons as for the first anomaly.
The method I used was fairly reliable; however, a few improvements could have been made such as controlling the variables. To keep the surface area the same, a special cutter could have been used to cut the Calcium Chloride marble chips into equal size and shape. This would have kept the surface area the same. Also, a temperature controlled environment would have controlled the temperature variable. These two improvements would have kept the experiment a fair test. Another improvement would be to use a set of scales that were more accurate than to 0.1g. This would ensure that each Calcium Carbonate marble chip was exactly 1g, but because I used a set of scales that were only accurate to 1g, the marble chips I used may have been slightly under or slightly over 1g. This would have affected my experiment.
