Need help on CIE Chemistry Paper 5!

[Deadly_king]

Nov. 2009 ppr52 Q1 (e)

Let's say the concentration stated above was 2.0 moldm^-3

You need to calculate what mass of the salt you would need to form 2.0 moldm^-3 solution.

Mr of the solid ethanedioic acid = 2(12) + 4(16) + 2 + 2(18) = 126

Conc in g/dm³ = Mr x Conc in moldm^-3
Hence Conc in g/dm³ = 126 x 2.0 = 252

In 1000 dm³ of solution, 252g of this solid will be required.

You need to prepare this solution of concentration 2.0 moldm^-3 in a 250cm³ graduated flask.
Hence you will need ( 252/1000 x 250 )= 63g of the solid

Procedure :
1. About 50cm³ of water were placed in a beaker.
2. 63g of ethanedioic acid were then added into the beaker.
3. Stir the mixture until all the solid dissolves.
4. Pour the acid solution in a 250cm³ volumetric flask.
5. Rinse the beaker with a small amount of water and pour the washings into the volumetric flask.
6. Bring up to the mark with distilled water.

Here is your required solution of ethanedioic acid of concentration 2.0 moldm^-3

Hope it helps