Preliminary method
- The variable that I am testing for is the concentration of acid. Therefore a range of different concentrations of acid is required. This can be done by starting with 2M acid and diluting it to the required concentration. Also an excess amount of carbonate would need to used.
- A conical flask with a delivery tube was set up. The conical flask was suspended underwater in a bowl of water via the delivery tube. An inverted measuring cylinder was placed on to collect any gas produced.
- Firstly, 10cm3 of acid was poured into the conical flask.
- Next, an excess amount of grounded carbonate was poured into the conical flask.
- Immediately after this, the conical flask was bunged and the measuring cylinder was left to collect any CO2 gas produced.
- Then, as the reaction had stopped reacting, the volume of CO2 produced would be measured
Conclusion and Evaluation
From the experiment that I have concluded that as the concentration of acid increases, the volume of CO2 produced also increases. Therefore, the graph showing this trend is a straight line. Also, if the concentration of acid was 0mol/litre (i.e water), there is no CO2 produced. Therefore, the line would cross the origin. Also, I noticed that as the volume of CO2 produced increased, a larger amount of gas was wasted according to the predicted amount. This is shown in the graph below:
The reason why more gas is wasted when a higher concentration of acid is used is because the reaction is more vigorous. Therefore, more CO2 is produced almost instantly. Therefore, before the bung could be put on, a lot of gas is wasted (according to theory predictions). This is the reason why more gas is lost as the concentration of acid increases.
With the results obtained, I can predict that as the concentration of acid increases the volume of CO2 produced also increases. However, the actual amount of CO2 produced would always be less than expected due precision and accuracy errors and the loss of gas. The percentage of error due to these reasons would be anything from 8% to 0.2%. I know this because the measuring cylinder has 2cm3 divisions and therefore a volume can be measured to the nearest cm3. The percentage from the highest value and lowest value was calculated according to theory.
The evidence obtained was sufficient to support the theory. I know this because the graph produced shows a clear trend in comparison to the predicted values according to the theory calculations. Therefore, the theory suggested has reason to be true and can be used to explain why the volume of CO2 differs when using different concentrations of acid. The percentage from the highest value and lowest value was calculated according to theory.
I can predict that as the concentration of acid increases the volume of CO2 produced also increases. However, the actual amount of CO2 produced would always be less than expected due precision and accuracy errors and the loss of gas. The percentage of error due to these reasons would be anything from 8% to 0.2%. I know this because the measuring cylinder has 2cm3 divisions and therefore a volume can be measured to the nearest cm3. The percentage from the highest value and lowest value was calculated according to theory.
Explanations
The volume of CO2 produced will change as the number of moles of acid used will change. The actual number of moles of acid can be determined by using the following formula:
Number of moles= volume x concentration
1000
By using the formula above, if the concentration of acid was to change the number of moles of acid used would also change.
If the number of moles of acid used were changed, the number of moles of CO2 produced would change. This would also change the volume of CO2 produced as 1 mole of gas occupies 24,000 cm3, therefore a different number of moles of CO2 would produce a different volume of CO2.
Improvements to the method:
A lot of gas was wasted in this experiment. Therefore the following set up may be used to minimise the effect of lost CO2. Basically, the conical flask will be pre-bunged to make sure that not CO2 is lost.
