Gravimetric Analysis

Question 1

Gravimetric analysis

Answer 1

a technique through which the amount of an analyte can be determined through the measurement of mass before and/or after a physical or chemical change.

Question 2

Analyte

Answer 2

Ion being analysed in gravimetric analysis

Question 3

Process of gravimetric analysis

Answer 3

1. Ensure that the volume of analyte is known
2. Add excess reagent to precipitate out all of the ‘active’ ions in the
   analyte (for example, AgNO3 to precipitate out Cl- ions)
3. Filter out the precipitate and discard the filtrate
4. Rinse the residue (precipitate) with distilled water and dry to constant mass (eg in a warm oven)
5. Weigh the precipitate and perform necessary calculations

Question 4

What could lead to a lower mass than expected?

Answer 4

• Incomplete precipitation due to variation in solubility
• Variation in solubility due to temperature
• Incomplete transfer of precipitate due to splashes, spilling and poor filtering
• not all active ingredient is filtered out

Question 5

What could lead to a higher mass than expected?

Answer 5

• Inefficient drying of precipitate as water results in higher mass
• measurement errors
• contamination of precipitate

Question 6

Precipitate

Answer 6

A solid that is formed in a reaction between two dissolved substances or gases

Question 7

Residue

Answer 7

Solid remaining in filter paper after filtration

Question 8

Filtrate

Answer 8

The liquid that passes through the filter paper during filtration