cycle of copper reactions

Experiment 3
A Cycle of Copper Reactions

Chemistry Department UCC

1st Year Practicals

Introduction n n n n n Copper is one of the most important metals.
Copper is reddish with a bright metallic lustre
It is malleable, ductile, and a good conductor of heat and electricity (second only to silver in electrical conductivity)
Its alloys, brass and bronze, are very important
Has various oxidation states: 0 in elemental copper, +1, and +2 which is observable in corroded brass/bronze

Oxidation states n n

n

Oxidation state is an indicator of the degree of oxidation of an atom
The formal oxidation state is the theoretical charge the atom would have of all bonds were 100% ionic
Oxidation is loss of electrons, reduction is gain of electrons (OIL RIG)

Oxidation States of Copper n n n n n 0

Cu

Transition metal – different oxidation states
Cu0
elemental state
Cu+1
Cu+2 most common
Cu+3/ Cu+4 unusual oxidation
- 2 electrons

2+

Cu

reduction
+ 2 electrons

0

Cu

Objectives n To observe a sequence of chemical reactions starting and finishing in elemental copper metal, and to practice quantitative laboratory techniques.

Cu → Cu(NO3)2 → Cu(OH)2 → CuO → CuSO4 → Cu
Cu(NO3)2 = copper nitrate
Cu(OH)2 = copper hydroxide

CuSO4 = copper sulfate
CuO = copper oxide

Experiment 1(a)
Cu + 4HNO3 → Cu(NO3)2 + 2NO2↑ + 2H2O
NO2 given off as a coloured gas*

H(NO)3

Transfer contents to beaker containing
100 mL of water
Cu
100mls H2O

Wash conical flask with 10 mL of water

*Carry out reaction in the fumehood

Experiment 1(b)
Cu(NO3)2 + 2NaOH → Cu(OH)2 + 2NaNO3
Add 30 mL of NaOH solution to the solution of copper nitrate from part 1(a) while stirring with a glass rod
A precipitate of insoluble copper hydroxide forms and settles to the bottom of the beaker Copper hydroxide precipitate Decant off the liquid, taking care not to lose
any