The Gravimetric Analysis of Chloride Salt
Gravimetric Analysis of a Chloride Salt
CHEM 1001
Purpose: To illustrate typical techniques used in gravimetric analysis by determining quantitatively the chloride content in an unknown soluble salt.
Theory: AgCl(s) is a very insoluble solid, yet still does have some solubility. Because of these traits, the following reaction is able to occur:
Ag+(aq) + Cl−(aq) → AgCl(s) .
This reaction is able to occur in both directions. When a soluble silver salt such as AgNO3 is added to a solution containing Cl−(aq) ion, then the added Ag+(aq) precipitates as AgCl(s) until all the chloride is consumed. For this particular reaction K sp = 1.6 x 10−10.
The reason why the solution is precipitated in an acidic medium become this causes the particle to dissolve faster, decreasing the time of reaction. This is the same reason why the solution is heated in order to coagulate because it speed up the particles inside the solution decreasing the time it needs to complete the reaction.
It is smart to use HNO3 when washing down the precipitate because when the AgCl(s) precipitates the particle decrease in size allowing it to pass through the filter paper. The precipitates are then heated in attempt to evaporate all the water until it precipitate is virtually entirely a solid.
Lastly, it is important that the AgCl(s) is placed in a dark space when not being used because of photodecomposition. This is the process that causes the solution to break down in the presence of light rays.
Procedure: 1) Gather unknown salt sample from TA and record its code number for future comparison.
Verify there are two glass filter crucibles in the desiccator that were previously in the 110°C oven.
Weigh out a sample of the unknown salt using an analytical balance anywhere between 0.1000g to 0.1500g and place in a labelled 250mL beaker.
Calculate the approximate value of 0.1M of AgNO3 that will be needed for the precipitation and add 5mL in excess to ensure all chloride are precipitated. (Volume
CHEM 1001
Purpose: To illustrate typical techniques used in gravimetric analysis by determining quantitatively the chloride content in an unknown soluble salt.
Theory: AgCl(s) is a very insoluble solid, yet still does have some solubility. Because of these traits, the following reaction is able to occur:
Ag+(aq) + Cl−(aq) → AgCl(s) .
This reaction is able to occur in both directions. When a soluble silver salt such as AgNO3 is added to a solution containing Cl−(aq) ion, then the added Ag+(aq) precipitates as AgCl(s) until all the chloride is consumed. For this particular reaction K sp = 1.6 x 10−10.
The reason why the solution is precipitated in an acidic medium become this causes the particle to dissolve faster, decreasing the time of reaction. This is the same reason why the solution is heated in order to coagulate because it speed up the particles inside the solution decreasing the time it needs to complete the reaction.
It is smart to use HNO3 when washing down the precipitate because when the AgCl(s) precipitates the particle decrease in size allowing it to pass through the filter paper. The precipitates are then heated in attempt to evaporate all the water until it precipitate is virtually entirely a solid.
Lastly, it is important that the AgCl(s) is placed in a dark space when not being used because of photodecomposition. This is the process that causes the solution to break down in the presence of light rays.
Procedure: 1) Gather unknown salt sample from TA and record its code number for future comparison.
Verify there are two glass filter crucibles in the desiccator that were previously in the 110°C oven.
Weigh out a sample of the unknown salt using an analytical balance anywhere between 0.1000g to 0.1500g and place in a labelled 250mL beaker.
Calculate the approximate value of 0.1M of AgNO3 that will be needed for the precipitation and add 5mL in excess to ensure all chloride are precipitated. (Volume
Bibliography: 1. Burk, R.C., M. Azad, X. Sun, and P.A. Wolff. "Gravimetric Analysis of a Chloride Salt." Introductory Chemistry: Laboratory Manual.