Experiment_13_-_Sample_Analysis

Experiment_13_-_Sample_Analysis - Chem istry 1B Experimen t...

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Chemistry 1B Experiment 13 61
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62 Chemistry 1B Experiment 13 Sample Analysis. Precipitates and Complexes of Silver Ion Data for Determining Formulas Solutions containing NH 3 , CO 3 2– , Cl , I , PO 4 3– , and S 2 O 3 2– ions were added to equal proportions of a silver nitrate solution, which contained the complex ion Ag(H 2 O) 2 + . All of the added solutions were also clear and colorless. AgNO 3 ( aq ) by itself Colorless solution AgNO 3 ( aq ) with NH 3 ( aq ) Colorless solution AgNO 3 ( aq ) with Na 2 CO 3 ( aq ) Pale yellow precipitate AgNO 3 ( aq ) with NaCl ( aq ) White precipitate AgNO 3 ( aq ) with NaI ( aq ) Yellow precipitate AgNO 3 ( aq ) with Na 3 PO 4 ( aq ) Yellow precipitate AgNO 3 ( aq ) with Na 2 S 2 O 3 ( aq ) Colorless solution Formulas of Silver Complexes and Precipitates Ag + ions formed precipitates with CO 3 2– , Cl , I , and PO 4 3– ions. Solids are electrically neutral; the charges of all their ions add up to zero. Therefore, the formulas of these precipitates are: Ag 2 CO 3 , AgCl, AgI, and Ag 3 PO 4 . It is not obvious from these observations that Ag + ions formed soluble complex ions with NH 3 and S 2 O 3 2– ions. However, data on the next page shows that solutions containing NH 3 and S 2 O 3 2– ions were able to convert the pale yellow precipitate Ag 2 CO 3 into colorless solutions. Thus, complex ions more stable than Ag 2 CO 3 must have formed. Ag + has a coordination number of 2, so it binds to two ligands when it forms complex ions. The formulas of the complex ions formed with NH 3 and S 2 O 3 2– are therefore: Ag(NH 3 ) 2 + and Ag(S 2 O 3 ) 2 3– . The product-favored reactions that occurred when NH 3 ( aq ) and Na 2 S 2 O 3 ( aq ) solutions were added to Ag 2 CO 3 ( s ) were: Ag 2 CO 3 ( s ) + 2 NH 3 ( aq ) → 2 Ag(NH 3 ) 2 + ( aq ) + CO 3 2– ( aq ) Ag 2 CO 3 ( s ) + 2 S 2 O 3 2– ( aq ) → 2 Ag(S 2 O 3 ) 2 3– ( aq ) + CO 3 2– ( aq ) Ag(H 2 O) 2 + ( aq ) Colorless solution Ag(NH 3 ) 2 + ( aq ) Colorless solution Ag 2 CO 3 ( s ) Pale yellow precipitate AgCl ( s ) White precipitate AgI ( s ) Yellow precipitate Ag 3 PO 4 ( s ) Yellow precipitate Ag(S 2 O 3 ) 2 3– ( aq ) Colorless solution
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This note was uploaded on 09/04/2011 for the course CHEM 1B taught by Professor Fossum during the Spring '10 term at Laney College.

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Experiment_13_-_Sample_Analysis - Chem istry 1B Experimen t...

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