Materials: Special Devices SD-606, see Figures. Either the horizontal stage or vertical stage model can be used.
Observations: Cell 1 clouds up from the formation of AgCl precipitate. Cells 2 and 3 remain clear; there is no CI- present in them.
Procedure: (a) Show rows of dominoes (chemical chains) started by various means, e.g., push one down, knock one down with a pencil, blow over, corresponding to various initiation mechanisms (light, heat, catalyst). (b) Insert pins in holes, blocking the falling of dominoes: corresponds to inhibitors breaking chains. (c) Add increasing numbers of pins. Show a point reached where every "chain" is broken by an inhibitor molecule, and that beyond this point the number of chains broken is independent of inhibitor concentration. If in breaking a chain the inhibitor molecule reacts (e.g., is oxidized) then an inhibitor concentration is reached (where all chains are broken by inhibitor) where the amount of inhibitor oxidized (by breaking chains) becomes independent of inhibitor concentration. This is in contradiction to Guldberg and Waage's Law of Mass Action, and is peculiar to certain chain reactions
Dem. 6 10ÑPhotogrophi Processes
Dem. 607-Copper
Wire Burned in Chlorine
Experiment developed by Raymond P. Garman. To show:
Copper burning in chlorine gas.
Materials: 10 in. of No. 20 Cu wire; 4-02 narrow neck, clear-glass, square hottle of chlorine gas; Bunsen burner.
To show: Development of the silver image, and solution of unchanged AgCl in photographer's fixer (hypo, NiteSzOa 5HzO).
-
Materials: AgNOg-aq, dil. HC1, Ka;S;Og-aq, cell C-4, stirrer. Procedure: Precipitate AgCl by mixing 30 ml water with 2 drops each of AgNOi-aq and dil. HC1, and distribute in the four cells of C-4. It should project light brown; if it is darker, dilute with water. Expose cells 3 and 4 to the light of the projector, shielding cells 1 and 2. Then pour 5 ml Na&Og-aq into cells 2 and 3. Stir. Compare the four cells. Observations Tube 1 is brown with AgCl. Tube 2 is clear since the AgCl has been dissolved by hypo. Tube 3 is slightly dark since the Ag formed by photodecomposition of AgCl is not dissolved by hypo. Tube 4 is darkest since it contains both Ag and AgCl.
+
-
+
Reactions: (a) Ag+ Cl- -+ AgCl. (b) 2AgCl light -+ 2Ag Clz. (c) AgCl 2 NiteSsOa NaAg(Si0a)z NaCl.
+
+
Dem. 6 1 1-Analysis
+
for Silver Group (1) Cations
Procedure: Coil half of the copper wire around a pencil. Project the bottle of chlorine gas. Heat the copper coil momentarily in the Bunsen flame (macro), then immediately lower the red hot coil into the bottle of chlorine
To show: The steps in routine analysis for Ag, Pb, and Hg (ous).
Observations: The copper glows as it burns in the chlorine, and a cloud of C u d z forms.
Procedures: (a) Precipitation of group. Project H-3 with the three culture tubes half-full of water. To them add 5 drops of AgNOg-aq, of Pb(NO&aq, and of HgNOg-aq respectively. Now add 2 drops of dil. HC1 to each tube. (b) Removal of P b and of Ag. Boil each solution; set aside tube 2. To tube 1 add 5 ml of NHg-aq. (c) Confirmation of cations. To tube 1 add 5 ml dil. HNO,. To hot tube 2 add 2 drops KiCrzOr-aq. To tube 3 add NH3-aq.
Dem. 608-Turpentine
To show:
Burned in Chlorine
Interaction of chlorine and turpentine.
Materials: 2-oz wide mouth square clear-glass bottle of Cl2 gas, stoppered; turpentine, cotton-tipped swab, 13 X 100 mm test tube, beaker of very hot water. Procedure: Warm 5 ml turpentine for 5 min in a test tube immersed in hot water. Project bottle of Clz, immerse swab in warm turpentine, thrust swab into bottle of Cl,. Observations: Turpentine smokes, then catches fire; black soot forms.
+ 8Ck
Reaction: CiOHu
-
10C
+ 16HC1.
2. CHLORIDES Dem. 609-Chloride
Content of Water
Experiment developed by Raymond P. Garman. To show: sources.
Chlorine content of water from different
Materials: Tapwater, distilled water, de-ionized water; C-3, stirrer, AgN03-aq. Procedure: Project C-3 with cells three-quarters full of tap, distilled, and deionized water, respectively. Add 3 drops of AgN03-aq to each. Stir. A310
/
Journal of Chemical Education
Materials: AgNOi-aq, Ph(NO&aq, HgN03-aq; cell H-3; dil. HCI, NHi-aq, dil. HNOa, KzCr2O7-aq.
Observatzons: (a) Precipitation of group. White AgCl, PhCL, and H ~ z C Iprecipitate; Z also show macro, (b) Removal of P b and Ag. Only the PbClz in tube 2 dissolves when the solutions are heated. The AgCl dissolves in NHi-aq t o form Ag(NH&+ ion. (c) Confirmation of catzons. The Ag(NHg) +Cl- solution reprecipitates white AgCl when HN0i is added. The P b + + precipitates yellow PbCQ. The HgzCIz,when NHg-aq is added, forms black Hg and white HgNHaCI precipitates Exhibit the precipitates macro. Dem. 6 12-Hydrolysis of SbCI, To show: Reversible hydrolysis, Procedure: Project C-3 quarter-full of SbC13-aq. Add 2 ml water to cells 2 and 3; stir. Add 2 ml conc. HC1 to cell 3; stir. Observations: SbClg
+ HiO
