Gravimetric Analysis Lab Report
GRAVIMETRIC ANALYSIS OF A CHLORIDE SALT
Report Submitted by: Ronald Milner
Laboratory partner: Kiesha Mantik
Lab Performed: February 16th, 2012
Group: Thursday Afternoon, Group F
Date submitted: March 14th, 2012
Purpose: To determine the chloride content of an unknown soluble salt while illustrating the techniques involved in gravimetric analysis.
Theory: In order to find the chloride content of an unknown soluble salt, that chloride can first be extracted from the solution in the form of a precipitate. While some substances are easily soluble in water due to molecular properties, others are not. These properties can be taken advantage of when trying to isolate a particular ion. By implementing …show more content…
This solubility can be shown by calculating the solubility product Ksp.
(1) AgCl(s) => Ag+(aq) + Cl-(aq) Ksp = [Ag+(aq)]·[Cl-(aq)] = 1.6 x 10-10
While silver chloride will be in equilibrium with its ions in the solution, because Ksp is so small, the dissolved ions can be considered negligible. When AgNO3 is added to a solution containing containing Cl- ions, a displacement reaction is undergone and the Ag+ and Cl- ions will precipitate out quickly as AgCl(s), until all of the Cl- is consumed (assuming Cl- is the limiting reagent).
A small amount of salt will be left in solution, depending on the amount of excess Ag+ added to solution. Because maximum solubility will occur when there is no excess Ag+ ion present, the Ksp value can be used to calculate the remaining Cl- in worst case conditions.
With no excess Ag+, [Ag+] = [Cl-]; let both = …show more content…
A hotplate was then prepared and set to heat to setting 5. While the hotplate was preheating, .1259g of unknown salt was then weighed by difference in a 250 ml glass beaker. 100 ml of distilled water was then added to the unknown sample and 1ml of HNO3 was added by a TA. The solution was then stirred. The necessary amount of AgNO3 needed for reaction was calculated as 19.5 ml along with an additional 5ml excess and 3ml for later use. The needed AgNO3 was then obtained from a TA. The calculated value of AgNO3 along with 5ml excess was added to the 250ml beaker containing the unknown sample and placed on the hotplate. The solution and precipitate was heated, with gentle stirring at intervals in order to encourage crystal formation. Several times the solution was overheated, releasing too much steam. When overheating occurred, the beaker was removed and the temperature of the hotplate was reset before placing the beaker back in its original position. When the majority of the precipitate had collected in larger pieces and the solution was semi-clear, the solution was tested for completeness of reaction with the previously collected 3ml of AgNO3. No precipitate formed and the reaction appeared complete. The 250 ml beaker was then placed in a drawer to cool out of direct light. The mass of the crucible was recorded as 19.3836 g and initials were written it in order to
Report Submitted by: Ronald Milner
Laboratory partner: Kiesha Mantik
Lab Performed: February 16th, 2012
Group: Thursday Afternoon, Group F
Date submitted: March 14th, 2012
Purpose: To determine the chloride content of an unknown soluble salt while illustrating the techniques involved in gravimetric analysis.
Theory: In order to find the chloride content of an unknown soluble salt, that chloride can first be extracted from the solution in the form of a precipitate. While some substances are easily soluble in water due to molecular properties, others are not. These properties can be taken advantage of when trying to isolate a particular ion. By implementing …show more content…
This solubility can be shown by calculating the solubility product Ksp.
(1) AgCl(s) => Ag+(aq) + Cl-(aq) Ksp = [Ag+(aq)]·[Cl-(aq)] = 1.6 x 10-10
While silver chloride will be in equilibrium with its ions in the solution, because Ksp is so small, the dissolved ions can be considered negligible. When AgNO3 is added to a solution containing containing Cl- ions, a displacement reaction is undergone and the Ag+ and Cl- ions will precipitate out quickly as AgCl(s), until all of the Cl- is consumed (assuming Cl- is the limiting reagent).
A small amount of salt will be left in solution, depending on the amount of excess Ag+ added to solution. Because maximum solubility will occur when there is no excess Ag+ ion present, the Ksp value can be used to calculate the remaining Cl- in worst case conditions.
With no excess Ag+, [Ag+] = [Cl-]; let both = …show more content…
A hotplate was then prepared and set to heat to setting 5. While the hotplate was preheating, .1259g of unknown salt was then weighed by difference in a 250 ml glass beaker. 100 ml of distilled water was then added to the unknown sample and 1ml of HNO3 was added by a TA. The solution was then stirred. The necessary amount of AgNO3 needed for reaction was calculated as 19.5 ml along with an additional 5ml excess and 3ml for later use. The needed AgNO3 was then obtained from a TA. The calculated value of AgNO3 along with 5ml excess was added to the 250ml beaker containing the unknown sample and placed on the hotplate. The solution and precipitate was heated, with gentle stirring at intervals in order to encourage crystal formation. Several times the solution was overheated, releasing too much steam. When overheating occurred, the beaker was removed and the temperature of the hotplate was reset before placing the beaker back in its original position. When the majority of the precipitate had collected in larger pieces and the solution was semi-clear, the solution was tested for completeness of reaction with the previously collected 3ml of AgNO3. No precipitate formed and the reaction appeared complete. The 250 ml beaker was then placed in a drawer to cool out of direct light. The mass of the crucible was recorded as 19.3836 g and initials were written it in order to