Chemistry lab 12 -postlab

Chemistry lab 12 -postlab - Co 2+ (aq)+7NO 2-(aq)+3K +...

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Post Lab Experiment 12: Qualitative Analysis of Cations (Part A) 1. a) Ag + is not soluble in HCl; it will form AgCl (s) b) Ag + is soluble in NH 3 ; it will form Ag(NH 3 ) 2 + (aq) c) Fe 3+ is soluble in HCl d) Fe 3+ is not soluble in NH 3 ; it will form Fe(OH) 3 (s) e) Co 2+ is soluble in HCl f) Co 2+ is soluble in NH 3 Since Fe 3+ is not soluble in NH 3 , it will precipitate out of the solution containing the three ions first. As a result, the presence of the Fe 3+ ion will be confirmed first, then with the addition of HCl, the presence of the Ag + will be confirmed next, since Ag + is not soluble in HCl. The Co 2+ ion will be confirmed last, following the same procedures as described in the lab. 2. Equation 6 represents a redox reaction:
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Unformatted text preview: Co 2+ (aq)+7NO 2-(aq)+3K + (aq)+2H + (aq) ↔ NO(g)+H 2 O(l)+K 3 [Co(NO 2 ) 6 ] (s) Co is being oxidized from an oxidation number of +2 to +3. N is being reduced from an oxidation number of +3 to +2. 3. The chloride ion came from the HCl that was added to the solution containing the three ions in the first step. It had reacted with the Ag + ion in the solution to produce AgCl (s), which was then dissolved in NH 3 (aq), where it dissociated into Ag(NH 3 ) 2 + (aq) and Cl-(aq), the chloride ion. The addition of nitric acid caused a reaction between NH 3 and itself, causing the Ag + ion to re-precipitate out of solution as AgCl....
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This note was uploaded on 02/25/2012 for the course CHEM 2142 taught by Professor Roberts during the Fall '10 term at Texas State.

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