Download The Discovery of Chemical Change Through the Chemistry of Copper Laboratory 02 1

Laboratory 02
The Discovery of Chemical Change Through
the Chemistry of Copper
1
Objectives
•Observe chemical changes through a series of chemical
reactions.
•Learn simple mass and volume measuring techniques.
•Understand and use the law of conservation mass.
•Learn the proper techniques for the handling and disposal of
chemicals
2
Law of conservation mass
Law of conservation of mass is a relation stating that in a
chemical reaction, the mass of the products equals the
mass of the reactants.
http://www.youtube.com/watch?v=dExpJAECSL8
3
Copper
Chemical element with the symbol Cu
Atomic number 29
Good electrical and thermal conductor
Pure copper is soft and malleable
An exposed surface has a reddish-orange tarnish
It is used as a conductor of heat and electricity,
a building material, and a constituent of various
metal alloys
4
Copper is an essential element for plants and animal, through not in
metallic form but as copper (II) ions.
Copper (II) salts contain the copper atoms in an ionized or charged
form and are typically blue to green in color.
5
The copper cycle
1
5
2
4
3
The cycle of copper reactions to be performed in this experiment
6
Reaction 1: Oxidation of metallic copper with nitric acid (HNO3)
Cu(s) + 4HNO3(aq)
Cu(NO3)2(aq) + 2NO2(g) + 2 H2O(l)
Oxidation
A common form of chemical reaction which is the combining of oxygen with various
elements and compounds.
Example:
The corrosion of metals is a form of oxidation, rust on iron for example is iron oxide.
Safety Issue: NO2 which is generated
during this experiment is very
dangerous. ADD NITRIC ACID IN A
HOOD! Do not walk around the room
with a flask that is evolving brown
NO2 gases!
7
Reaction 2: Converting copper nitrate to copper hydroxide
Cu(NO3)2(aq) + 2NaOH(aq)
Cu(OH)2(s) + 2NaNO3(aq)
8
Reaction 3: Converting copper hydroxide to copper oxide
Cu(OH)2(s) + heat
CuO(s) + H2O(l)
Dehydration
involves the loss of
water
9
Reaction 4: Converting copper oxide to copper sulfate
CuO(s) + H2SO4 (aq)
CuSO4(aq) + H2O(l)
Most metal oxides are basic oxide and react with acids to form salts and
water: metal oxide + acid --> salt + water.
10
Reaction 5: Converting copper sulfate back to copper metal
CuSO4(aq) + Zn(s)
ZnSO4(aq) + Cu(s)
Add dilute hydrochloric acid (HCl) and stir to dissolve any excess zinc.
Zn(s) + HCl (aq)
ZnCl(aq) + H2(g) Hydrogen gas is highly flammable and will
burn in air at a very wide range of
concentrations between 4% and 75% by
volume.
After this point the solid, pure copper can be isolated, dried
and weighed.
http://en.wikipedia.org/wiki/Hydrogen
11
Weigh and calculate the mass of copper recovered and your
percent yield using the following equation:
12
Safety Notes
· Wear safety glasses at ALL TIMES.
You will be using nitric, sulfuric and hydrochloric acids as well
as sodium hydroxide all are damaging to skin, clothing and
especially your eyes.
· Perform Reaction 1 in a fume hood. Toxic NO2 is produced.
· Hydrogen gas is evolved in Reaction 5.
Keep your apparatus away from open flames.
13
14