The other independent variable was the hydrochloric acid as we changed it to 2M. We also changed the way we put the calcium powder first and then put the hydrochloric acid after, as we established that it would facilitate the process and assure better results. It would be easier to quickly place the bung inside to prevent the gas from escaping. We also timed the readings of the gas 10 – 120 seconds. The reason why we left it to 120 seconds is to give us a better understanding of the results.
If we allowed up to 60 seconds, the results would not enable us to see whether the reading of the gas was going slow or carried on increasing.
However, in the preliminary experiment we did not do the temperature of hydrochloric acid. This could be the reason why the results for the actual experiment were much better and reliable Table 1. The results for the preliminary experiment. Calcium Powder (1g) 1m Hydrochloric acid (50ml) 1m Time Reading Of Gas 10 22 20 37 30 39 40 42 50 44 60 44 70 44 80 44 90 44 100 44 110 44 120 44 Evaluating preliminary of calcium powder 1g and 1m of hydrochloric acid 50ml.
Table 2 shows the reaction between calcium powder and hydrochloric acid. We can see that the readings on the gas were going very fast.
I can see this as the results show the reading of the gas at 10 seconds immediately jumped to 22, and then increased to 50 seconds of a reading of 44. They then stayed the same till 120 seconds. Consequently, to see whether the reading of the gas slowed down and gave us better results, we decided to change the hydrochloric acid to 30 ml and have it 2M instead of 1.
Table 2. Preliminary of calcium powder and hydrochloric acid Calcium Powder (1g) Hydrochloric acid (30ml) 2m Time Reading Of Gas.
Evaluating preliminary results of 1g of calcium powder and 30ml of 2M hydrochloric acid. In Table 3 I have experimented 1g of calcium powder and 30 ml of 2M hydrochloric acid. As you can see in this table the reading of the gas went even faster than the first experiment we did because this time the reading of the gas jumped to 42 from just 10 seconds and then stayed at 54 at 60 seconds till 120 where we ended the timing. The fact that it stopped at 54 shows that reaction was not very affective as at first the readings would go very fast then slow down towards the end.
To balance this out we thought we should keep the same about of hydrochloric acid and M but change the calcium powder to 1. 5g for the next experiment. Also the method of putting the calcium powder first and then put the hydrochloric acid after which we did for experiment one and two, we will change this in experiment two to see if it gives a better result. Table 3. Evaluation: Prelimiary results of calcium , powder and hydrochloric acid. Calcium Powder (1. 5g) Hydrochloric acid (30ml) 2m Time Reading.
Evaluating results for preliminary of 1. 5g of calcium powder and 30ml of 2M hydrochloric acid. In this table I have experimented 1. 5g of calcium powder and 30 ml of 2M hydrochloric acid. For this experiment we can see that it did jump massively to 58 in 10 seconds but as the seconds go by the reading of the gas gradually increases. This enabled us to have a better understanding of how much mass of calcium powder and how much volume of hydrochloric acid we needed. These results came out the best so the amount of mass and volume we used was good.
The other reason why it could have given us a better result is because of the method we used to do the experiment as we changed it to putting the hydrochloric acid first then adding the calcium powder, the reason why I think it helped doing the routine this way is to ensure the gas does not escape and that’s why a good set of secure results came up. Evaluation of preliminary From the preliminary I have learnt that 2M is best suited for the surface area. The preliminary helped us decide what amount of mass of each calcium chips is needed, and the volume of the hydrochloric acid.
In this preliminary I have also concluded how long we timed each rate of reaction was to stay the same, for the main experiments of surface area, and concentration. This is because 120 seconds, gives us a lot of time, to find out if the reading of the gas gradually increases, or if it just stops, and in the 3rd experiment it showed that the reading of gas gradually increased, which is why it turned out to be the best method in addition to this we will keep the time to 120 seconds as it will allow me to see the increasing rate of reaction and 12 results should be enough to identify any trends.
The other thing that we learnt from the preliminary is the routine of the way we poured the hydrochloric acid first, and then quickly added the calcium powder, this gave us a better result, and we will continue this routine for the main experiment of surface area and concentration. From the preliminary we also realised that we did not take the temperature of each experiment, and we should do it for the main experiments, as it will tell us if the change of temperature affects the reaction, and it will enable us to control the temperature as well so the results are accurate and reliable.
In the preliminary for each experiment we repeated the process only once, we will change this amount of repeats to 5 times in the main experiments for both surface area and concentration. This is because it allowedus to calculate an average rate of reaction. This will ensure that there are no abnormal results and it will increase accuracy. Justification of Method: The first method in doing the experiment is measuring how much mass is wasted as carbon dioxide produces. In the second method we put the calcium carbonate and the hydrochloric acid into the conical flask and measured the mass of C02 being produced.
We then placed the cotton wool covering the reactant. Meanwhile the gas beame heavier as it accumulated while being formed. When the cotton wool is taken off the mass decreased and the gas was being released. Then when the gas escapes one can see how much gas was formed. This will be placed on a balance so that I am able to measure how much gas is lost and record this at regular intervals such as every 10 seconds. The disadvantages of this method is that it is not an accurate way of recording how much gas is released as the balance may only notice small amounts of carbon dioxide in weight being let off by the reaction.
Using a gas syringe would make a more precise reading of the experiment The issues that may occur in this method is that there is only a small amount of volume of gas that is escaping which leads there being no change in the mass of the reactant therefore there will be nothing to plot when we do our graphs. In addition to this the other problem that may occur is that there might be issues with the measuring with a balance and there will not be sufficient balances to carry out the experiment. The second method is measuring and collecting a gas product.
This method is carried out by placing the reaction mixture in a beaker attached to a tube going through the water into the measuring cylinder. The gas will then escape from the reactant in the measuring cylinder and I will record the volume of gas at consistent intervals such as every 10 seconds. The issues that may happen in this method is, when you are flipping the gas cylinder andfilling with water over, the risk of a lot of water may escape beforehand. Consequently, it will affect your results as more gas is wasted, meaning less is formed and barely any carbon dioxide will flow through the tube.
The third method is timing how long it takes for a small amount of solid of reactant to disappear. For this method, the hydrochloric acid and calcium carbonate will be placed in the conical flask and the timer will be started. The timer will then be stopped when I can no longer see any solid. However, if I use this method I will not be able to draw a graph as I only have 2 results- the start and finish of the experiment. Even though these methods will eventually give me the results , I believe they will not give me the best results. The method we choose in our group was the gas syringe.
I will be using a gas cylinder with rubber tubing attached to the conical flask with the reaction taking place. We then recoded results as we went through every experiment. I then measured how much gas was produced and recorded the reading regularly on a stopwatch. I will also repeat the experiment 5 times to make sure that are results were precise and reliable. The other reason why we chose this method is because it was more difficult to carry out the experiment and set the experiment up and the other methods will not make our experiment very accurate making our results unreliable.
The issues that might occur in this method is that there is not a variety of things you can do to find about the rate of reaction as you can only measure the time it takes and the volume of carbon dioxide being produced. . The apparatus I will use will look like this: I believe that this apparatus will enable me to collect the most precise results. My equipment is: 1. Measuring Cylinder: This piece of equipment was the best choice for my experiment because we had to use this to measure the exact amount of hydrochloric acid to get accurate results.
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