Calcium Carbonate + Hydrochloric acid Calcium Chloride + Water + Carbon Dioxide
CaCO3 + 2HCl CaCl2 + H2O + CO2
Prediction
I predict that if the concentration of the Hydrochloric acid is doubled then the experiment will happen twice as fast. This is because twice as many HCl particles will be present than previously, and there will be twice as much chance of the calcium carbonate chips colliding with the concentrated hydrochloric acid. Therefore, when the concentration is double, the time taken for the reaction should be halved. When the surface area of the calcium carbonate chips is doubled there will be twice as much chance of it colliding with the Hydrochloric acid. Therefore I predict that when the surface area is doubled, the time taken for the experiment is halved. A temperature increase of 10 C will see the time taken for the experiment halved because energy of collisions in the particles increases, this means that there are going to be more successful collisions.
Research
A reaction occurs when particles collide. This process is based on random particle movement. So therefore, the more particles you have in a space, the more likely they are to collide. Therefore making the reaction accelerate. This theory can be proved if you compare the rates of reaction with marble in hydrochloric acid. 'If the acid is of a higher concentration, the reaction will be quicker. Also if the particles have more energy, they will be travelling faster, making them collide more frequently.
Variables/Factors
Variables
1. The amount of marble chips will not vary because more marble chips would produce more gas when put into the HCL, so a weaker concentration of acid, could end up looking stronger than a stronger concentration of acid.
2. The amounts of acid will not vary because more of a weaker concentration could be as strong as a little of a stronger concentration, which would make an unfair test.
3. The strength of the acid WILL vary because the whole point of the experiment is to see how much gas is produced at different concentrations of acid.
4. The apparatus used will be the same every time because other pieces of apparatus may have a different scale, the syringe may be stiffer. Etc.
5. The time between measurements will not change so you can see how much gas is produced in the same amount of time.
6. The temperature will have to be the same in each experiment because 10
Factors
1. We will take measurements every 10 seconds
2. We will use the same amount of acid each time.
3. We will use the same equipment every time after thoroughly washing it out when
we have completed 1 experiment.
4. We will measure gas produced by the reaction between the marble chips and acid.
5. The gas will be measured in cm3
6. The marble chips will be measured
This helps to do the experement because it gives a firm and decisive decision about the amount of mass and the mesaurments that are going to be taken at certain points. It makes sure we have a firm guidelines for our exoeriment when we do it . also, when we are writing the project , we can think the experiment through thorougly and we may not be able to do that when we are doing the experiment
conclude from my results that acid concentration does effect the rate of reaction. My graph clearly shows that as the concentration of the acid was increased the reaction took place in less time. There is a significant difference between the amount of time taken from the lowest concentration to the highest concentration of acid. The graph is not linear and there is a slight curve in the results, this shows that the rate was not proportional and the rate of the reaction changed. This may be because of a change of temperature in the room during the experiment. It also may be because the reaction was not instantaneous and it took a second or two for the reaction to speed up, this is described as an exponential rate. As the results from the three experiments I did were almost exactly the same I only used one graph which shows the average of all of the results.
Evaluation
The experiment went very well. There was one anomalous result in the last concentration. In both experiments 2.5 molar started slower than the 2 molar but then got quicker than the 2 molar at the end. (You can see ive circled this in the graph) Although I have some ideas which may gain a more accurate reading. Firstly, the surface area of the marble chips were not perfect. It could have been made better if I had used powdered marble chips because the surface area of each wieght of powder would have been a lot similar. If I did use Powder however, the concentration of acid may have had to be weakened as the reaction would have taken place a lot quicker due to the very large surface area and readings wouldn't have been as accurate. Secondly, an inaccuracy may have been caused by the fact that the temperature may have dropped during the reaction. This could have been used if I used a water bath to heat up the acid to a constant temperature. You have to allow for a margin of human error during the experiment, some people react slower than others and you have to rely on the person taking the readings with the stopwatch. The results were reliable because they were almost the same in both experiments, even though there was an anomalous result; it happened in both experiments, so the results were still relibale, I have no explination for the anomalous result.
