The volumetric flask and the pipette were washed out with distilled water to ensure that there were no impurities.
This solution was then poured into a volumetric flask. The beaker was washed out with more distilled water which was than added to the volumetric flask, this was to ensure that any solution that had been left behind was not lost. The volumetric flask was then filled to exactly 100ml using the pipette. It was important not to go over the 100ml mark at all. The bottom of the meniscus should be on the line of the volumetric flask. The stopper was then put in the volumetric flask and this was then inverted 2-3 times to mix the solution around. If it was just shaken it would not have mixed sufficiently. The burette was then washed out with distilled water as was the small beaker. The small beaker was then washed out with a small amount of hydrochloric acid to ensure that none of the water was left behind. The same thing was done for the burette. The burette was then filled with about 40ml of hydrochloric acid. This was left for about one minute to ensure that all of the hydrochloric acid has settled in the burette and that none was still on the sides of the tube. Once it had sufficiently settled the reading was taken, this reading is the initial burette reading. Again it is important to take the reading which is at the bottom of the meniscus!
The conical flask was then washed out with distilled water. Using the pipette exactly 10ml of the sodium chloride solution was then transferred into a conical flask. The bottom of the meniscus should be on the mark for 10ml. When transferring this into the conical flask a tiny amount of solution will be left in the pipette which is impossible to get out. However you must ensure that you get as much solution out as possible by touching the end of the pipette into the solution which is in the conical flask. This will pull as much solution out of the pipette as possible. The tiny bit left over is accounted for because the mark on the pipette allows for it.
Once 10ml of solution are in the conical flask, two drops of screened methyl orange indicator should be dropped into the solution. If less than two drops are added the solution may not be dark enough to see the colour change, and if more than two drops are added the water in the indicator may cause the solution to become too dilute. A white tile must be placed under the conical flask so that the colour of the solution can be easily seen. The burette tap must then be turned slowly to allow only a few drops at a time of hydrochloric acid out. One the solution in the conical flask appears to be getting lighter the speed at which the tap is turned must slow down even more. As soon as the solution goes clear no more hydrochloric acid must be added. The reading is then taken off of the burette and this is recorded as the final burette reading. This reading must be taken from the bottom of the meniscus.:
The whole experiment is repeated three times to get accurate results.
Experiment number 1 and 2 gave accurate results, number 3 however was 0.1 off of the other two. Therefore I shall take the average only of experiment numbers 1 and 2 and use these to calculate the concentration of the hydrochloric acid.
The average of 26.8 and 27.05 is 26.925. Na2CO3 + 2HCl = 2NaCl + H2O + CO2
One mole of Na2CO3 reacts perfectly with two moles of HCl.
I used 10ml of a 25 dm3 solution of Na2CO3. This reacted with exactly 26.925ml of an unknown concentration solution of HCl.
Being as one mole of sodium carbonate reacts with two moles of hydrochloric acid we can divide 26.925 by 2 to get the value of one mole of hydrochloric acid. This gives us 13.462
Therefore:
10ml x 26.925 = 269.25
13.462 x 269.25/13.462 = 0.269
The concentration of the hydrochloric acid is therefore 0.269/dm3.
