Volumetric Analysis Practicals

Method

1. Weigh accurately (to two decimal places) between 5.10g and 5.50g of anhydrous sodium carbonate in a weighing bottle. -Fill up the weighing bottle away from the scales so that any spilt sodium carbonate a) does not react with the scales and b) affect the weight.
2. Transfer the sodium carbonate, in small portions, to a 100cm3 beaker and dissolve in distilled water, using a stirring rod to aid dissolution. -Be sure to rinse the weighing bottle out with the distilled water and pour it into the beaker in order to get all of the sodium carbonate.
3. Transfer the solution to a 250cm3 volumetric flask, using the funnel and stirring rod as shown below. –Make sure all solution goes into the volumetric flask by, again, rinsing apparatus with distilled water into the funnel.
4. Make the volume up to 250cm3 using distilled water.

Results

Calculation

Mol = M/mr = 5.4/106 = 0.0509

Concentration = Mols Dissolved/Volume

Conc. = 0.0509/(250/1000) = 0.2036

Therefore         concentration= 0.204 mol dm -3(3.s.f)

Questions

1. Anhydrous sodium carbonate is a primary standard. Find out and write a few sentences describing what a primary standard is.

These are chemicals that are available in a pure form that can be weighed out in appropriate molar quantities and dissolved and made up to the correct volume to make a standard solution.

2. If your sodium carbonate had been impure, what effect would it have had on the final concentration of the solution you made up?

The concentration would be less as although the same quantities of sodium carbonate would be weighed out, as it is impure and not all sodium carbonate there will e less in the solution. And there will be other substances present in the solution.