Procedure: (a) Mix in culture tube by shaking 0.5 g 1 g NaOH 1 g KN03. Project in H-3 pyrolusite and heat until molten. Cool. Shake with 30 ml water, filter equal amounts into the two cells of C-2. Project. (b) Gently add a dropperful of dil. HNOa to the liquid in cell 2. (c) Drop a small lump of dry ice into cell t.
Note: Mohr's salt, (NH4)2FeSO~,6H20 can be used in place of FeS04.
Observations: (a) KNOa oxidizes MnO, to green manganate, K2MnOl. (b) HN03 oxidizes the upper portion of the liquid in cell 1 to purple permanganate, MnOn-. (c) Dry ice converts green M n O r into purple permanganate, Mn0,- (this is an industrial method).
Materials: dil.
+
+
+
Reactions: 3KZMnO4 2COz MnOz.
+
Reference: 1959.
-
2KMn04
HARPIN, R. E., J. CHEM. EDUC.,
+ 2KzCOa 36,. A685,
Dem. 645-Oxygen from KMn04 To show: The preparation of oxygen from heating permanganate. Materials:
Procedure: Project H-1 with the test tube quarterfull of KMnOa. Heat with the small alcohol burner. Collect the evolved gas and test it for oxygen with a glowing splint. Observativns: Oxygen gas is evolved, the splint bursts into flame.
-
To shm: oxide. Materials: MnOz.
+ 4MnOn + 301
Dem. 646-MnOz as a Catalyst lor H,O, Decomposilion Catalytic action of MnOz on hydrogen perC-3, two splints, 3% H202, detergent,
Procedure: Project C-3 half-filled with HzOz. (a) Wet two sticks, dip into MnOZ to collect some particles, drop the sticks into cells 2 and 3. (b) Drop some granules of detergent into cell 3. Observations: (a) Vigorous decomposition of the HzOz occurs on the surface of the MnOz particles. (b) As the O2gas evolves, i t rises with the detergent as a foam.
+
Fe(llJ Dem. 647-Permongonote To show: Titration of ferrous salt with standard permanganate solution.
Materials: 0.5 N FeSOa, (NH&S04.6HzO [98.04 g per 1000 ml solution], dil HzS04, C-1, stirrer, 0.1 N KMn04 (3.16 g KMnO6 per 1000 ml solution). Procedure: Project C-1 half-full of water. Add a dropperful of dil. H2S04. Drop in (class counting) 20 drops of 0.1 N KMnO4. Now drop in (class counting) the FeS0, solution until the pink color vanishes. Reactions: lOFeSO4 2MnS04 8HzO
+
+
-
2KMn04 + 8HzS04 ++ 5Fez(SO&
A496 / Journol of Chemicol Education
'2-3, KMnO,, NaHS03-aq, NaS-aq, HzSOr
Procedure: Project C-3 with cells quarter-full of dilute H2S04. Add varying amounts of dil. KMn04 to each cell. Now titrate with NaHSOa-aq or NaS-aq. Observations: The violet KMn04 is reduced to colorless (pink) Mn+=,according to reaction as 5S01
+ 2KMnO. + 2&0
KzSOl
-
KBO,
+ 2MnSO. + 2H9S04
+
Dem. 649-Pernungunate M02 To show: Titration of hydrogen peroxide with standard permanganate solution. 0.1 N KMnOl, dil. HzSOI, 3% HzOZ,C-1,
Materials: stirrer.
H-1, KMnOl, splint.
4 K M n 0 ~ 2K10
+
Dem. 648-Pernmganate SOzor HzS To show: The reduction of Mn04- by SOz or HzS.
Procedure: Project C-1 half-full of water. To it add a dropperful of dil. H2S04 exactly 10 drops of KMnOl. Now add HzOadropwise until the pink color disappears.
+
+
-
+
+
Reaction: 5H202 2KMnOa 3H,S04 2 ~ k 3 0 , KzS04 Hz0 502 t . Calculations: 0.1 N KMnO, contains 3.16 g KMn04 per 1000 ml solution. From the volume of solution of in the original soluHz02 used, calculate the % HH,02 tion.
+
+
E. Group VIII. (Fe, Go, Ni) Dem. 650--Oxidation and Reduction of Iron Experiment developed by Edwin H. Cooper. To show: Fe(II1).
The oxidation of Fe(I1) and reduction of
-Materials: Soln A: 0.4 g Mohr's salt (Fe(NH,),SOn,6Hz0) 4 m16 M HzSOI 100 ml water. KMnOp-aq, K2Crz0i-aq,KSCN-aq, iron picture-wire; H-3.
+
+
Procedure: Project culture tubes one-quarter full of 1 ml KCNS;aq (mixture should be pracSoln A tically colorless.) (a) Now add dropwise 60 red color KZCrzO7-aqto tube I , KMnOa-aq to tube 8, and HzOz to tube 3. (b) Put 1-in. lengths of iron picture-wire into each tube and boil 1 min.
+
Observations: (a) I
