Gravimetric Analysis

Question 1

Uses of gravimetric analysis

Answer 1

1. To determine the percentage of moisture
2. To determine the percentage of sulphur dioxide in the atmosphere
3. To determine the percentage of phosphorus in fertilizers
4. To determine the amount of chloride ions in water

Question 2

What happens in volatization gravimetric analysis?

Answer 2

In this method, the substance being analyzed is converted into a gas by either directheating or reacting the substance with a chemical to release the gas.

Question 3

How to calculate the % purity?

Answer 3

(6.93/7) x 100

Question 4

Apparatus used in gravimetric analysis

Answer 4

Suction funnel
Suction flask
Silica crucible
Sintered glass crucible

Question 5

Properties of suction flask

Answer 5

conical in shape and made from heavy glass material
has a sidearm to attach to a pump, suction funnel is attached to the top of the suction ask

Question 6

Silica crucible properties

Answer 6

made from ceramic and is used to dry the precipitate by heating
can withstand high temperatures

Question 7

Properties of sintered glass crucible

Answer 7

used to filter, dry and weigh

by using this device losses in the mass of precipitate are kept to a minimum; made from glass

has a porous disc made from sintered ground glass fused to its base

can withstand temperatures up to 200oC

Question 8

Properties of the precipitate formed when precipitating agent reacts with substance being analyzed

Answer 8

• Must be easily filtered
• Have a very low solubility
• Must be easy to wash free from impurities
• Must be unreactive with substances in the atmosphere
• Must be of known composition after drying

Question 9

Types of gravimetric analysis

Answer 9

1. Precipitation gravimetric analysis
2. Volatalization gravimetric analysis

Question 10

What happens in precipitation gravimetric analysis?

Answer 10

In this method, the substance being analyzed is converted into a sparingly soluble precipitate by adding an excess of a precipitating agent.

Question 11

Procedure of precipitation gravimetric analysis

Answer 11

1. A fixed amount of the substance being analyzed is dissolved in distilled water
2. An excess amount of the precipitating agent is then added to the solution.
3. The mixture is then filtered by vacuum filtration. The container is rinsed with distilled water and the rinse is filtered.
4. The precipitate is washed with distilled water.
5. The precipitate is then dried by heating to a constant mass.
6. The dry solid is weighed.