gravimetric analysis

Question 1

what does heating to constant mass involve

Answer 1

• heat a substance
• allow to cool in a dessicator to prevent absorption of water
• weigh
• repeat the steps of heating and cooling and weighing until no further changes in masses are observed

Question 2

what is gravimetric analysis used for

Answer 2

determining the mass of an element or compound in a substance

Question 3

how can you readily isolate and purify a substance

Answer 3

by converting it into another substance of known chemical composition

Question 4

how can you convert a substance into another substance of known composition

Answer 4

through precipitation or volatilisation

Question 5

what occurs in precipitation conversion

Answer 5

• the substance undergoes a precipitation reaction
• precipitate is separated from the filtrate and the filtrate is tested to ensure the reaction has gone to completion
• the precipitate is washed and dried to a constant mass and then weighed

Question 6

what occurs in volitalisiation conversion

Answer 6

• the substance is heated and any volatile products (often water) are evaporated
• the substance is heated to a constant mass and the final mass is recorded