What are the key sources of error in gravimetric analysis?

In gravimetric analysis, errors can occur at different stages, affecting the accuracy of results. The key sources of error are:

1. Incomplete precipitation:
   • If the reaction does not go to completion, some analyte remains in solution.
2. Impure or contaminated reagents:
   • Impurities can form extra precipitate or interfere with the reaction.
3. Loss of precipitate:
   • During filtration, washing, or transfer, some precipitate may be lost.
4. Co-precipitation:
   • Other substances may get trapped in the precipitate, increasing its weight.
5. Adsorption of moisture or gases:
   • The precipitate may absorb water or carbon dioxide from the air, changing its mass.
6. Incomplete drying or decomposition:
   • If the precipitate is not dried completely or decomposes on heating, the mass will be incorrect.
7. Weighing errors:
   • Using an inaccurate balance or improper handling can lead to errors in measurement.

In short:
Errors in gravimetric analysis come from incomplete reactions, impurities, loss of material, moisture, decomposition, and weighing mistakes, all of which affect accuracy.