Concentration of sodium carbonate solution:
Calculating the number of moles first:
Relative formula mass ( RFM ) of Na2CO3 : ( 23 x 2 ) + 12 + ( 16 x 3 ) = 106g
Amount of sodium carbonate used at the start of the experiment was 2.65g.
Number of moles = 2.65
106
= 0.025 moles
250 cm3 divided by 1000 = 0.25dm3.
Therefore the concentration of the sodium carbonate solution is:
Concentration (in mol dm-3) = Number of moles (in mol)
volume (in dm3)
= 0.025
0.25
= 0.100 mol dm-3
The concentration of the sodium carbonate solution that I made up is 0.1 mol dm-3 .
Concentration of sulphuric acid:
As I know from the equation that I stated at the start of the analysis one mole of sodium carbonate reacts with one mole of sulphuric acid, the ration being 1:1. This is the point at which neutralization occurs and the solution became clear.
I can use the same equation for calculating the concentration of the acid solution, as I did for the sodium carbonate soluiton. The only difference is that not all of the sodium carbonate was used for each titration. Only 25cm3 was used each time not the 250cm3 that was calculated as the one mole.
So to work out the number of moles of sulphuric acid that it needed to be able to neutralise the sodium cabonate solution, you divide the number of moles for the 250cm3 sodium carbonate solution by 10. As 250 ÷ 10 = 25cm3.
Number of moles of H2SO4 = 0.025
10
= 0.0025 moles
I will now have to use the following formula to calculate the concentration as before:
concentration (in mol dm-3) = Number of moles (in mol) ÷ volume (in dm3)
The volume that is needed in this equation was the average titre that was calculated for the experiment. In this case it was 19.7cm3. Which needs to be turned into dm3, which is done by dividing it by 1000.
19.7 ÷ 1000 = 0.0197 dm3
Concentration of H2SO4 = 0.0025
0.0197
= 0.127 mol dm-3
So the concentration of the sulphuric acid solution needed to neutralise 25cm3 of sodium carbonate solution is 0.13 mol dm-3 .
Therefore, 19.7cm3 of sulphuric acid with a concentration of 0.13 mol dm-3 , neutralises 25cm3 of sodium carbonate solution with a concentration of 0.1 mol dm-3 .
I think my results are accurate and reliable as all my results for the titre were close to each other, only having a difference of 0.1 cm3. My result shows that the concentration of sulphuric acid is 0.13 mol dm-3 .
This is not an exact value of the concentration of the acid, but it does agree with the statement at the start of the experiment, that it is between 0.05 and 0.15mol dm-3.
The main reason for my results not being completely accurate is due to human error. This will be explained further in my evaluation.
