I will measure the quantities of Ca CO3 using a balance. This would be much more accurate than adding the same number of spatulas each time. Also I will use a measuring cylinder to measure the HCl; this is more accurate than a beaker, as beakers do not have as many ‘measure lines’ as a measuring cylinder.
Prediction
I predict that as the concentration of the acid increases the amount of time it takes to collect 100cm³ of CO2 will decrease. This is because of the collision theory. As there will be more acid particles in the came amount of volume in the higher concentrated acid. As there are more particles to react with in the higher concentrated acid there is more chance for the acid and calcium carbonate particles to collide together.
Equipment list
Balance, conical flask, Ca CO3 , HCl, Rubber bung, rubber tubing, stopwatch, large beaker, retort stand, boss, clamp, measuring cylinder, water, thermometer.
Diagram
Method
Firstly I shall measure out my acid using a measuring cylinder. I will use 25ml of different concentrations of Hydrochloric acid. I will then put the acid into the conical flask. I then will measure out 2g of calcium carbonate. I will fill the large beaker and the measuring cylinder full of water. I will then put my hand over the top of the measuring cylinder to prevent any water from escaping and air entering. I will then tip the measuring cylinder upside down and place it in the beaker full of water. However if I loose too much water from the measuring cylinder I will fill the cylinder back up and retry until there is no air inside the upright measuring cylinder. I will then set up my retort stand, boss and clamp so the measuring cylinder is held up by the clamp, (as above.) I will then put one end of the rubber tubing into the bung and the other securely up the measuring cylinder. I shall drop the calcium carbonate into the HCl at place the rubber bung firmly in the conical flask. As soon as this is done I shall start the timer. Once the measuring cylinder has collected 100cm³ of carbon dioxide I shall stop the timer. I will record my time to the nearest second. I shall repeat this once more with each concentration, with 6 different concentrations.
Results
Conclusion
My results show that HCl reacts faster with Ca CO3 when the concentration of the acid is higher. As the concentration of the acid increases, the reaction time decreases. The higher the concentration the faster the reaction happened this is because it reacted with the same amount of Ca CO3 in a quicker amount of time than the lower concentration acid. The lower concentrated acid reacted in a slower amount time than the higher concentrated acid. This means the lower concentration took a longer time to react with the same amount of Ca CO3 therefore the lower concentration is not as reactive as the higher concentration. The average time taken for the reaction to finish declines from 0.25m to 1.5m. The only pattern I can find in my results is that all the average times are all smaller than the average time before it at the lower concentration.
The rate of reaction for each concentration.
My graph of the rate of reaction shows that as the concentration increases so does the rate of reaction. This means that the reaction would happen with more speed if the concentration of the acid is increased. CO2 was given off much quicker in the higher concentration, this means the reaction is happening faster. The reaction is happening faster as the concentration increases because there are more HCl particles in the same amount of space as before. The Ca CO3 is more likely to collide with an HCl particle in higher concentration than in lower concentration. The more particles present, the more likely they are to colliding with the Ca CO3 and forming a bond. The rate of reaction for the concentration of 0.75m appears to be anomalous. This is obvious on my graph. This may be because the acid was not 0.75m; from the graph it seems that the acid was slightly stronger. Also the rate of reaction for 1.5m is surprisingly high.
On my graph the gradient of the stronger concentrated acids are steeper than the weaker acids and are flatter towards the end of there reaction. My results support my prediction. My prediction stated that as the concentration of the acid increases the amount of time it takes to collect 100cm³ of CO2 will decrease.
Evaluation
My method worked well. The only drawback to my method was making sure there was no air in the upturned measuring cylinder. If I were to repeat this experiment then I would measure the weight loss of the conical flask to see how much CO2 has been released. This is an alternate way of measuring the reaction, without having to upturn the cylinder. I am happy with the consistency of the temperature of the HCl. My results are accurate; however I do appear to have results that are anomalous, which are prominent in my graph. For example the results for 0.25m at 7 minutes, and 0.5m at 7 and 8 minutes are inconsistent and stand out on the graph. These could have occurred if the conical flask was shaken during the experiment. I repeated all of my results a second time none of my results were drastically out of place however there were some which perhaps more inconsistent than others. If I were to repeat the experiment I would make sure that I repeated the experiment three times instead of just 2. Although this would take up much more time, I feel it more important to obtain the most accurate results possible. In addition, out of pure interest I would like to find what happens when the temperature of the HCl increases. To do this I would heat the acid to different temperatures at regular intervals and add the same amount of Ca CO3. I expect to see that as the temperature increases so does the reaction time. My precise results enable me to come to strong conclusion that the higher the concentration of HCl the less time was taken to collect 100cm³ of CO2 when reacted with Ca CO3.
