I will also use a stopwatch to record the time of how much gas has been made. I will record the readings at 30-second intervals.
I chose magnesium strips, as it is easy to measure the length of the strip using a ruler and therefore I would know how much magnesium I am using.
I also chose the metal ‘calcium carbonate’ in both large and small granules so that I can see the difference in the rate of the reaction between the two sizes.
I also chose iron fillings as it is easier to weigh than Iron Wool.
I will also add zinc to our metals as I will want a wide range of metals to choose from, I will use Zinc powder, as granules aren’t all the same size, and it is easier to weigh.
I chose a range of sulphuric acid as it would be a fairer test choosing a range rather than a cluster, therefore getting a range of results, I also will use the maximum and the least possible for our experiment so we could see a range of results.
THE METHOD The method that I chose was the Gas Syringe Experiment, as this is a very simple one to do and we can take as many readings as possible. This also has an accurate reading and its limit is 100ml (1ml). This is also very reliable as no gas can come out; it is airtight. The way this experiment works is that the reaction taking place in the conical flask will produce a gas which will be measured the gas syringe.
Preliminary experiment Results
First test: Hydrochloric acid 2 molar (50ml) and magnesium powder (1.5 grams)
From this we learned that 1.5 grams of magnesium was too much. Therefore we used a smaller amount of magnesium (0.5g)
Second test: Hydrochloric acid 2 molar (50ml) and magnesium powder (0.5 grams)
Again the reaction was too fast so we decided not to use magnesium powder. We also found that 2 molar was too fast. As I had already reduced the amount of magnesium powder to 0.5g I decided to reduce the Concentration of the magnesium to 1.0 molar.
Third test: Hydrochloric acid 0.2 molar (50 ml) and zinc powder (0.5 grams)
From this I had found that zinc reacts slowly. Hence I decided not to use it in the real experiment
I then used the metal ‘Calcium Carbonate’ in 0.5g
Fourth test: Hydrochloric acid 1.0 molar (50ml) and calcium carbonate powder (0.5 grams)
From this we found out that 1.0 molar was too fast so we decided not to use it.
Fifth test: Hydrochloric acid 0.2 molar (50 ml) and calcium carbonate powder (0.5 grams)
I found out that this was the experiment that I was going to rely on for my investigation therefore I will try a range from 0.2 – 0.8m for hydrochloric acid with calcium carbonate at 0.5 g.
Sixth test: Hydrochloric acid 0.4 molar (50 ml) and calcium carbonate powder (0.5 grams)
This worked really well. Had a good set of results
Seventh test: Hydrochloric acid 0.6 molar (50 ml) and calcium carbonate powder (0.5 grams)
Eighth test: Hydrochloric acid 0.8 molar (50 ml) and calcium carbonate powder (0.5 grams)
I will be investigating the rate of reaction between:-
0.5g of Calcium Carbonate and 50ml of Hydrochloric Acid (4 concentrations)
The Balanced Symbol and Worded equations for this reaction are:
Calcium Carbonate +Hydrochloric Acid ➔ Calcium Chloride + Carbon Dioxide + Water
2CaCO3(s) + 4HCl(aq) ➔ 2CaCl2(aq) + 2CO2(g) + 2H2O(l)
This is a list of my equipment that I will use and the reasons of why I chose them.
This is a list of the factors that may affect my results, and how they would affect them. Also on how I would control the factors in order to make the test fair.
These are the results I got from carrying out my actual experiment. I repeated each experiment 4 times to improve the reliability of the results. I also included an ‘Average’ column for each 30-second time interval, which I plotted onto the graphs in the previous pages.
Red font = outlier
Table 1: - Showing the volume of gas produced by a reaction between calcium carbonate and a 0.2M concentration of acid.
Table 2: - Showing the volume of gas produced by a reaction between calcium carbonate and a 0.4M concentration of acid.
Table 3: - Showing the volume of gas produced by a reaction between calcium carbonate and a 0.6M concentration of acid.
Table 4: - Showing the volume of gas produced by a reaction between calcium carbonate and a 0.8M concentration of acid.
These results were plotted onto graphs. The x-axis displayed the time (in seconds) and the y-axis displayed the average volume of gas produced (in cm³) for each 30-second interval. These graphs also included curves of best fit (to highlight the general trend of the reaction), range bars and an initial rate of reaction gradient.
Graph 1 shows a very sharp increase in the average volume of gas produced for the first 30 seconds as the plot on the line is very high up. These first 30 seconds are also where the rate of reaction is at its highest because there are more hydrochloric acid and calcium carbonate particles there to collide with each other to form the products of the reaction: calcium chloride, carbon dioxide and water. After the 30-second mark, the rate of reaction decreases as the line gets less steep. This is because by the 30-second mark there would be less hydrochloric acid and calcium carbonate particles available to collide with each other as some of these particles have already reacted to form calcium chloride, water and carbon dioxide gas. Thus, a smaller amount of products would be formed, causing the rate of reaction to slow. In the graph it is noticeable that there is a positive correlation, the longer the duration of time, the higher the average volume of gas produced. The range bars for the first five intervals are big – meaning that they aren’t completely reliable as there is a quite a big scatter of data. However, gradually, the range bars are smaller suggesting that these results are reliable due to the smaller scatter of data.
This trend is similar for the other four graphs – each graph has a point where the rate of reaction is at its highest and a point where the rate of reaction gradually begins to get lower.
There is also a trend between the acid concentration and the volume of gas produced. For instance, looking at Table 1, the average volume of gas produced at 120 seconds is 26cm³, but the for Table 2, the average volume of gas produced at 120 seconds is 29cm³ therefore signifying the fact that it is higher. From this, I can concur that, the higher acid concentration used, the larger average volume of gas is produced at the same time interval.
To conclude, there is a correlation between the, factor I am investigating and the initial rate of reaction. You can judge this by looking at table 5 – the higher the acid concentration, the faster the initial rate of reaction. We can tell as the higher the hydrochloric acid concentration, the more acid molecules there are to collide and therefore react with the calcium carbonate particles. This would produce a larger volume of hydrogen gas in the same amount of time – therefore increasing the rate of reaction.
Table 5: Showing the initial rates of reaction (cm³/s) for the different acid concentrations (M).
I calculated the initial rate of reaction for each graph by dividing the average volume of gas produced at the 120-second mark for that particular graph by 120. I decided to calculate the initial rate of reaction using the 120-second mark because this is a point where the rates of reaction for each acid concentration were still rising steadily, making it fair.
This is a diagram explaining how the increased molar of concentration of hydrochloric acid would result in more collisions with the Calcium carbonate particles.
Although I managed to obtain a good set of results from carrying out the experiment, there were several difficulties in trying to collect valid and reliable data. The following table describes the problems I encountered while carrying out the experiment, and suggestions on how I would improve the experiment if I had to repeat it.
Additionally, I would improve the experiment by using a longer measuring duration than two minutes as the reactions never stopped, they had only slowed down. This is reflected on Graphs 1-5 – the curves of best fit were never flat and thus suggesting that the reaction never stopped, but in truth, the reaction would have stopped sooner or later.
Confidence on the Conclusion
Generally, I am quite confident with my conclusion. I attained a set of results which strongly suggested that the concentration of acid has an effect on the rate of the reaction. Although, as most of the graphs show, many of the range bars are a bit large, meaning that the results are not very reliable as there is a large scatter of data, perhaps this was because the rubber cork was not sealed as tightly for these experiments, or I took longer to place it back on to the top of the conical flask hence, causing some of the product gas to escape, justifying the reason why its results was so scattered.
Throughout the experiment, I had obtained many outliers in my results, as shown by Tables 1-4. These may have occurred because of any of the following reasons:
- On some repeats, I did not seal the rubber bung as quickly as I did on other repeats or I did not seal it as tightly, causing more hydrochloric acid to escape into the room and therefore making the reading in the gas syringe less than what it would have been.
- Not all of the remaining hydrochloric acid from the previous repeat was washed out of the conical flask – making the rate of reaction for the next repeat faster
Despite these outliers, the majority of the averages were close to or on the curve of best fit, so after eliminating outliers, the results were reliable on the whole.
Here's what a teacher thought of this essay
This is a reasonably well written laboratory report. It uses the appropriate level of scientific terminology with spelling punctuation and grammar of a generally good quality. Good features and further improvements have been suggested throughout.