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This guide outlines practical strategies for creating qualitative goals in chemistry. It describes methods for identifying specific ions by conducting tests on various solutions, including HCl, NaOH, NH4OH, and more. By leveraging unique properties of chemicals, we devise tests that yield observable outcomes, such as color changes or precipitate formations. The analysis involves understanding solubility, acid-base, and complexation equilibria, ensuring accurate results in qualitative chemical assessment.
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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 ______
