Question

10.

Potash is a common name for potassium carbonate. Originally, potash was obtained by
adding water to the ash produced from the burning of wood, filtering and evaporating the
filtrate.
(a)
Meirion was asked to find the percentage of potash that could be obtained from some
wood ash. He added water to a known mass of wood ash, stirred the mixture and then
filtered the product. The filtrate was then made up to a volume of 250 cm³.
(i) State why the mixture was stirred.
[1]
E
(ii) Describe, giving full practical details, how the volume was made up to exactly
[4]
250 cm³.

Answer 1

(a) (i) The mixture was stirred to ensure that the wood ash was completely mixed with the water, allowing for the maximum amount of potash to be dissolved and filtered out of the ash.

(ii) To make the volume up to exactly 250 cm³, Meirion can use a graduated cylinder or a measuring cylinder to measure the volume of the filtrate. He can then add distilled water to the filtrate until the total volume reaches 250 cm³. He can use a dropper or a pipette to add small amounts of water and stir the mixture until the desired volume is reached. He can also measure the volume with a graduated cylinder or a measuring cylinder. Finally, he can check the final volume of the solution again to make sure that the volume is exactly 250 cm³.