Unit 3

Question 1

Gravametric analysis of a precipitation reaction?

Answer 1

The substance undergoes precipitation reaction. Precipitate is separated from the filtrate. Filtrate is tested to ensure the reaction has completed. The precipitate is washed, dried to constant mass and weighed.

Question 2

Gravametric analysis volatilisation?

Answer 2

Substance is heated to constant mass to remove water.

Question 3

What is heating to constant mass?

Answer 3

Involves heating a substance to over 100oC, and then cooling in a desiccator. The desiccator prevents the reabsorption of water. The substance is then weighed and then heated again. Repeated until there is a constant mass.

Question 4

A primary standard must:

Answer 4

Have high purity, stable in solid and solution, be soluble, have a reasonably high gfm

Question 5

A standard solution is prepared by:

Answer 5

Weighing a known mass of solid accurately, dissolving the solid in a small volume of deionised water (in a beaker), transferring the solution into a standard flask and adding rinsings, making up to the graduation mark with deionised water, stoppering and inverting the flask to mix.