Analysis of Silver in an Alloy
Analysis of Silver in an Alloy
Introduction
In this experiment an alloy of silver will be analyzed to determine its silver content. The silver-copper alloy will be dissolved in nitric acid, the silver will be precipitated as silver chloride, and the silver chloride will be filtered, washed, dried and its mass determined. From the mass of the silver chloride formed and the mass of the original sample, you will be able to calculate the percent of silver in the alloy. Because the results are based on the mass of a product, this procedure is classified as a gravimetric analysis.
Silver and copper are very nonreactive metals. Neither will dissolve in hydrochloric acid or sulfuric acid. The "oxidizing" acid nitric acid, HN03, is required. In acidic solutions the nitrate ion is an excellent oxidizer, and it will oxidize Ag(s) to Ag+(aq) and Cu(s) to Cu2+(aq). The reduction product is the gas NO. As the colorless nitrogen monoxide gas forms, it immediately reacts with the oxygen in the air to produce the orange-brown gas N02. The half-reactions for the oxidation of silver and copper by nitric acid are as follows:
Ag(s) → Ag+(aq) + e-
Cu(s) → Cu2+(aq) + 2e-
4H+(aq) + NO3- (aq) + 3e- → NO(g) + 2H2O(l)
Once the silver and copper ions are in solution, they can be separated from each other by precipitating the silver ions as silver chloride. Silver chloride (AgCl) is very insoluble in water, while copper(II) chloride (CuCl2) is soluble. The addition of chloride ions to the solution will precipitate essentially all of the silver and none of the copper. The silver chloride precipitate is then filtered from the solution.
Experimental Methods
Follow protocol as listed for Laboratory Experiment #1 in “Experiments for Advanced Placement Chemistry” by Sally Ann Vonderbrink, Ph. D. With these modifications: instead of using a Gooch Crucible and fiber glass pad, we used a Buchner Funnel and filter paper.
Theoretical Methods
Balance out the half
Introduction
In this experiment an alloy of silver will be analyzed to determine its silver content. The silver-copper alloy will be dissolved in nitric acid, the silver will be precipitated as silver chloride, and the silver chloride will be filtered, washed, dried and its mass determined. From the mass of the silver chloride formed and the mass of the original sample, you will be able to calculate the percent of silver in the alloy. Because the results are based on the mass of a product, this procedure is classified as a gravimetric analysis.
Silver and copper are very nonreactive metals. Neither will dissolve in hydrochloric acid or sulfuric acid. The "oxidizing" acid nitric acid, HN03, is required. In acidic solutions the nitrate ion is an excellent oxidizer, and it will oxidize Ag(s) to Ag+(aq) and Cu(s) to Cu2+(aq). The reduction product is the gas NO. As the colorless nitrogen monoxide gas forms, it immediately reacts with the oxygen in the air to produce the orange-brown gas N02. The half-reactions for the oxidation of silver and copper by nitric acid are as follows:
Ag(s) → Ag+(aq) + e-
Cu(s) → Cu2+(aq) + 2e-
4H+(aq) + NO3- (aq) + 3e- → NO(g) + 2H2O(l)
Once the silver and copper ions are in solution, they can be separated from each other by precipitating the silver ions as silver chloride. Silver chloride (AgCl) is very insoluble in water, while copper(II) chloride (CuCl2) is soluble. The addition of chloride ions to the solution will precipitate essentially all of the silver and none of the copper. The silver chloride precipitate is then filtered from the solution.
Experimental Methods
Follow protocol as listed for Laboratory Experiment #1 in “Experiments for Advanced Placement Chemistry” by Sally Ann Vonderbrink, Ph. D. With these modifications: instead of using a Gooch Crucible and fiber glass pad, we used a Buchner Funnel and filter paper.
Theoretical Methods
Balance out the half