experiments: gravimetric analysis

Question 1

what is “weighing by difference”?

Answer 1

record:

-weigh the container on its own
-weight of container and sample
-weight of container (and remaining sample) after transferring sample to beaker

-the mass of the container can be subtracted from the mass of the container + sample to obtain the mass of the solid itself.

Question 2

what is “weighing accurately approximately”

Answer 2

The exact mass should be measured
and should be close to x grams

Question 3

how do you heat to a constant mass?

Answer 3

-heat substance

-allowing to cool in a desiccator to prevent absorption of water

-weighing

-repeating the steps until no further changes in mass are observed.

Question 4

what is gravimetric analysis used to determine?

Answer 4

the mass of an element or compound in a substance

Question 5

what is the substance converted into?

Answer 5

another substance of known chemical composition, which can be readily isolated and purified

Question 6

How can the conversion occur?

Answer 6

either through precipitation or volatilisation

Question 7

describe the process of precipitation conversion

Answer 7

-precipitation reaction

-the precipitate is separated from the filtrate

-filtrate tested to ensure the reaction has gone to completion

-the precipitate is washed, dried to constant mass and then weighed

Question 8

describe the process of vocalisation conversion

Answer 8

-the substance is heated and any volatile products (often water) are evaporated.

-the substance is heated to constant mass and the final mass recorded

Question 9

what is a desiccator?

Answer 9

its used to provide the dry atmosphere