CHEM 7LM Lecture 3: Lecture 3
30 Aug 2016
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Qualitative analysis - set of analytical techniques to separate and identify chemical species in a sample. Instrumental methods (vs) quantitative analysis - set of analytical techniques that determines the amount of components in a sample. "semimicro" level- 1-2 mg of ion in ~5ml. Step 1: ions are removed in groups from the initial aqueous solution ie. group 1: ag+, hg22+, pb2+ (precipitated in hcl) Group 2: bi3+, cd2+, hg2+, sb3+/sb5+, sn2+/sn4+ (precipitated in h2s at ph=0. 5) Step 2: testing is conducted for the individual ions in each group ie. selective precipitation, ph control, complex ion formation, redox reactions. Increases hydrogen ions [h+]/decreases hydroxide [oh-] d/t strong acid (decreases ph) Dissolves insoluble carbonates [co32-], hydroxides, chromates [cro42-], and some sulfates [so42-] d/t //something about the strong acid reacts w/ base nature// Increases chloride ions [cl-]/precipitates insoluble chlorides d/t solubility rules (more ions pushes reaction towards precipitate) Destroys hydroxo (oh-) and ammine (nh3) complexes d/t strong acid (readily reacts with base)
