Technician 1 of 1
Practical 5.8 Stabilising an unusual oxidation number:
chromium(II) ethanoate, Cr2(CH3CO2)4(H2O)2
Purpose
Safety
To carry out experiments to:
(iii) prepare a sample of a complex,
e.g. chromium(II) ethanoate
[5.3.2g]
Throughout this experiment, you must wear eye protection.
The chemicals and procedures used in this experiment are
extremely hazardous, so you must take even more care than
usual to reduce risks from them by using suitable control
measures. Solid sodium dichromate(VI) is very toxic and
oxidising and is classed as a category 2 carcinogen. It is
an irritant to all tissues and you must wear gloves when
handling this solid. Avoid inhaling any tiny crystals. Zinc
powder is highly flammable. Concentrated hydrochloric acid
is corrosive. The hydrogen evolved is extremely flammable. As
hydrogen is evolved, naked flames must be kept clear.
Each group of students will need:
Eye protection
Gloves
Ground glass joint flask, 50 cm3, and apparatus as in the
diagram below
Measuring cylinder, 10 cm3
Beaker
Boiling tubes (32) in rack
Access to:
Rough balance
Concentrated hydrochloric acid, 20 cm3 corrosive
Zinc granulated, 1.5 g
Zinc powder, 3 g highly flammable
Sodium dichromate(VI), 1 g very toxic (category 2
carcinogen), oxidising
Sodium ethanoate, saturated solution, 10 cm3
approximately
5 M HCl
sodium
dichromate(VI),
zinc, water
sodium ethanoate
solution
Edexcel practical materials adapted from Nuffield Advanced Chemistry materials
255