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Qualitative Practical. Designing Your Own Qual. Goals. You will have ___________ solutions in ______________________ test tubes You need to identify which test tube contains each: HCl, NaOH, HCl, NaCl, H 2 O, CH 3 COOH, AgNO 3 , & NH 4 OH. In qual.
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Qualitative Practical Designing Your Own Qual
Goals • You will have ___________ solutions in ______________________ test tubes • You need to identify which test tube contains each: HCl, NaOH, HCl, NaCl, H2O, CH3COOH, AgNO3, & NH4OH
In qual • We make use of the specific __________ and ___________ properties of various ______ and ______ to devise tests that enable us to determine whether or not each of the ions is present. • Usually these tests consist of _________________ whose outcomes permit us to draw specific ______________________. • Often, in order to see the _______ we use the ___ _______________, where ___________ is formed.
Example A (gas). • Suppose we have a solution that we suspect to contain ammonium ion, NH4+. • Ammonium ion + hydroxide ions lead to formation of ___________________. • NH4+ + OH-→ ______________ + H2O • The _________________ could be detected either by ______or _________________ to the _______ that escape from the solution (red litmus turns blue). • If no ammonia present, then ____________ and ____________________________.
Example B (solid). • Solid (precipitate) formation. • To solution with suspected silver ions add HCl • Ag+ + Cl-→ • Not only silver forms ______________________ with chloride, but also Hg22+ and Pb2+. • So if a __________________ does form, it suggests the presence of at least one of these cations. • This is one of the obstacles of Qual analysis.
Qual approach • Sometimes the ________of one precipitate obscures the color of the other. • For example, PbS is ______ and Sb2S3 is _________. • So if you have both present, you see _ • To resolve such difficulties, the qual analysis of a sample is usually approached ________________. • First, reactions are carried out to _______________ from each other. • Then, the tests are performed to ________________ ___________________________________________
LeChatelier’s principle in qual. • The separations demonstrate the concepts of __________ ___________ and Le’Chatelier’s principle, which states that if a _________ is placed on a system, then the system ________ to minimize the effect of that _______. • The idea of _____________________ one way or another is frequently used in qualitative analysis experiments. • Qualitative analysis separations usually involve one of three types of equilibrium:
Solubility Equilibrium: • AgCl (s) ↔ Ag+ (aq) + Cl- (aq) • The solubility of AgCl will be _________ by addition of Cl- in form of HCl. • Cl- from the HCl is the same as Cl- from the ___________ • The AgCl solubility is shifted to the ___ when HCl is added
Acid-base equilibrium • NH3(aq) + H+(aq) ↔ NH4+(aq) • Adding acid (H+) shifts equilibrium to the ___________
Complexation Equilibrium • Ag+ (aq) + 2 NH3 (aq) → Ag(NH3)2+ • If the amount of ammonia is decreased the equilibrium is shifted to the ______
