L6 Qualitative Analysis

L6 Qualitative Analysis - CHEM 6BL Experiment 5:...

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CHEM 6BL Experiment 5: Qualitative Analysis Instructor: Dr. Sandrine Berniolles Page 1 Chemistry 6BL Lab/Course Schedule Week of Lecture & Exam Schedule Lab Period Lab Schedule Prelab & Report Due Dates May Qualitative 1 st lab End Experiment 4C Expt. 4A 1 11 Analysis (Expt. 5) 2 nd lab Expt. 5 (Parts I-II, Group A) Report Prelab Expt. 5 Chemistry 6BL Lab/Course Schedule Week of Lecture & Exam Schedule Lab Period Lab Schedule Prelab & Report Due Dates May Atomic 1 st lab Expt. 5 (Part II, Group B) ----- 2 May 18 Atomic Spectra (Expt. 6) 2 nd lab Expt. 5 (Part II, Group C) Expt. 4A-C Paper General Areas of General Areas of Analytical Chemistry Analytical Chemistry Qualitative Analysis Identification of materials present in the sample Quantitative Analysis Determination of the amount of material present in the sample 3
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CHEM 6BL Experiment 5: Qualitative Analysis Instructor: Dr. Sandrine Berniolles Page 2 Experiment #5 : Qualitative Analysis Relevant Concepts/Topics: Aqueous Equilibria & Solubility Le Chatelier’s Principle (H S 2H + +S 2 4 Le Chatelier’s Principle (H 2 S 2 H + S 2- ) Redox Reactions (in acid or base ) More Inorganic Complex Chemistry Goal: identify metal ions in an unknown ion solution (detective work) Qualitative Analysis Similar to Gravimetric Analysis ( Exp’t #1 ) in that precipitation is involved 5 But Gravimetric Analysis is quantitative You will use your knowledge of precipitation and K sp values to identify various metal ions qualitatively Qualitative Analysis: ID'ing Ions In this experiment, you will investigate a mixture of ten common metal ions: 2 6 Ag + , Hg 2 2+ Cu 2+ , Bi 3+ ,{Sn 4+ } Mn 2+ , Zn 2+ , Ni 2+ , Fe 3+ , Cr 3+
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CHEM 6BL Experiment 5: Qualitative Analysis Instructor: Dr. Sandrine Berniolles Page 3 Solubility Rules 7 Experiment #5 : Groups A : Groups A-C 10 metal ions separated into 3 major groups : “Group A”: Ag + , Hg I 2 2+ Cl renders insoluble (insoluble chlorides) 8 “Group B”: Cu 2+ , Bi 3+ , {Sn 4+ } H 2 S renders insoluble (insoluble acidic sulfides) “Group C” - Mn 2+ , Zn 2+ , Ni 2+ , Fe 3+ , Cr 3+ OH or S 2– (basic) renders insoluble (insoluble hydroxides and basic sulfides) Equilibrium Equilibrium Constant Constant Equilibrium Constant Determine whether a reaction tends to go toward products (“going forward”) or toward reactants (and “no going” 9 reactants (and not going ) K c = [products] [reactants] Solubility Product When reactants are a solid (e.g., an insoluble salt), [reactants] term drops out (K sp )
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CHEM 6BL Experiment 5: Qualitative Analysis Instructor: Dr. Sandrine Berniolles Page 4 K c & K sp Examples K = [SO 2 = 0 041 2 SO 2 (g) + O 2 (g) 2 SO 3 (g) 10 Ag + (aq) + Cl - (aq) AgCl(s) c 3 ] 0.041 [SO 2 ] 2 [O 2 ] K sp = [Ag + ][Cl ] = 1.6 10 -10 (favors reactants) Equilibrium Composition 11 Favors Reactants Favors Products Reaction Reaction Product Product Equilibrium Constant It is a constant : K c or K sp never changes Rt i d t Q 12 Reaction product Q C Same form as K, but arbitrary stage of reaction Plug concentration values into Q c Compare Q c to K c to determine whether
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This note was uploaded on 09/17/2009 for the course CHEM CHEM 6BL taught by Professor Berniolles during the Spring '08 term at UCSD.

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L6 Qualitative Analysis - CHEM 6BL Experiment 5:...

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