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Study Plan for Practical Work
Brady's solution can be difficult. The solution made up by my technical staff according to the instructions gave no sign of reaction. A 50:50 mixture of this solution and 1M sulfuric acid readily produces the precipitates seen in the video.
The Tollen's reagent will need to be made up freshly before the class and care is needed for its disposal. The silver mirror is much more impressive if the test tubes used are scrupulously clean.
Students need to be reminded about bumping. Without proper care, the heating of the dichromate mixture often leads to the contents of the test tube being ejected.
Materials:
| Propanone (5 cm3) | Propanal (2 cm3) |
| 0.1 M sodium dichromate (1 cm3) | 1 M sulfuric acid (15 cm3) |
| Benedict's solution (6 cm3) | 0.04 M sodium hydroxide (6 cm3) |
| Tollen's reagent (10 cm3) | Brady's reagent (10 cm3) |
| 0.01M iodine in KI (2 cm3) | |
| Test tubes (8) and rack | Boiling tubes (2) |
| 400 cm3 beaker | Bunsen burner |
| Heat-proof mat | Tripod |
| Gauze | Dropping pipettes |