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 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, NH 4 +. Ammonium ion + hydroxide ions lead to formation of ___________________. NH OH - → ______________ + H 2 O 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 Hg 2 2+ and Pb 2+. 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 Sb 2 S 3 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 NH 3 (aq) + H + (aq) ↔ NH 4 + (aq) Adding acid (H + ) shifts equilibrium to the ___________

Complexation Equilibrium Ag + (aq) + 2 NH 3 (aq) → Ag(NH 3 ) 2 + If the amount of ammonia is decreased the equilibrium is shifted to the ______

To obtain correct results