5 ml 6 d4' HC1 in C-2. Add a few granules of Zn. When react,ion ceases, add more granules. Continue uutil the solution becomes clear and projects well.
-
-
+
+
+
Sn++ Sn Zn++; and Zn Observations: Zn 2H+ Zn++ HI. AS the bubbles of Hz form, they pull the tin to the top as a spongy mass. After about four additions of Zn the solution clears and projects well.
+
Dem. 632-Amphoteric
Sn(OH),
Experiment developed by S. 8. Dunham and L. P. Johnson (Princeton-63). To shozu: droxide.
The amphoteric properties of stannous hy-
Materials: C-3.
SnC12-2H20dil. HC1, NaOH-aq, stirrer,
Procedure: Dissolve 1 g SnCI2.2H20in 50 ml water. Project C-3 with each cell half-full of this solution. (a) Now add NaOH dropwise with stirring, to cell 2 until a precipitate persists, and to cell 3 until the precipitate which first forms, redissolves. (b) Reverse the process by adding HC1 drop-wise, with stirring, until both cells 2 and 3 are clear. (c) Leaving these same solutions in the cells, repeat cycle (a, b). Observations: What occurs is explained by the following expressions: NaOH
SnCb
NaOH
Sn(0H). ?jc NalSn01
HCL
HCl
Dem. 633-Amphoteric
Ph(OHJ2
Experiment developed by Alphonse Palermo. To show:
The amphoteric properties of lead hydroxide.
Materials: Pb(NO&aq, stirrer, C-3.
NaOH-aq, dil. HN03-aq,
Procedure: Project C-3 with each cell half-full of water. Into each put 5 drops Pb(NO&aq. (a) Now add NaOH dropwise with stirring to cell 2 until the precipitate persists. To cell 3 add NaOH-aq. until the precipitate which first forms re-dissolves. (b) Reverse the process by adding dil. HN03 to cells 2 and S until they are clear. (c) Repeat cycle by adding NaOH-aq, then dil. HNOl to cells 2 and 3. Observations: What occurs is explained by the following expressions: OHOHPb'+
Dem. 634-Lead
= H+
Pb(OH)>~5 P b O i H*
Chromate versus Barium Chromate
To show The formatiou of chromates of lead and barium, and the difference in their solubilities in acid. Materials: Pb(NO&aq, HOAc-aq, stirrer, C-2.
BaCL-aq, I
