10b: Preparing and assessing the purity of an organic solid

Question 1

once the impure solid is obtained what do we do

Answer 1

We purify the solid

Question 2

dissolving in a minimum amount of hot solvent (water)

Answer 2

This dissolves both the products and impurities. dissolves soluble impurities. The minimum amount and shows all of the product is crystallized when cooled and it ensures a maximum yield.

Question 3

filtration (Usually through a hot funnel)

Answer 3

this removes any insoluble impurities. And the product remains dissolved. It also prevents crystals reforming

Question 4

cool the filtered solution by inserting the beaker in ice

Answer 4

This ensures all of the compound(product) recrystallizes, the crystals will reform but soluble impurities will remain in the solution.

Question 5

suction filtration with a büchner funnel to separate out crystals

Answer 5

This draws away any solvent/soluble impurities. A water pump is connected to the flask this reduces pressure and speeds up filtration

Question 6

Washing the crystals with distilled water

Answer 6

This removes any excess solvent/soluble impurities

Question 7

Dry the crystals using absorbant paper/filter paper

Answer 7

This removes excess water as water will affect the percentage yield of the crystals. You can use a desiccator/oven to remove water

Question 8

What does a small percentage yield suggest

Answer 8

That crystals were lost during washing/some products remains dissolved in the solvent/side reactions have occurred

Question 9

What does a greater than 100% percentage yield suggest

Answer 9

The product is not dried fully that for water has been left over in the product increasing the yield