1. Introduction to Chemical Reactions: Copper Cycle
1. There are several ways to classify chemical reactions
2. The goal of this experiment is to review several classes of chemical reactions: combination, decomposition, single replacement, double replacement, and acid/base neutralization.
3. The reactions will be performed in a specific order and, when completed, will regenerate the starting material, pure copper. Since you will not add copper to the reaction at any point after the initial step, it should be possible to recover all of the copper at the end of the cycle, thereby illustrating the Law of Conservation of Mass.
4. You are asked to practice your observational skills by recording the changes that occur at each step of the cycle. Color changes, the generation of gases or precipitates and changes in temperature are all examples of the types of phenomena you should be looking for when studying chemical reactions.

2. Specific Reactions
Cu(s) HNO3(aq) > Cu(NO3)2(aq) NO2(g) H2O(l)
Brown NO2(g) is quite toxic; reactions must be done in hood
Concentrated HNO3(aq) is corrosive and oxidizing; wash immediately if you get any on your skin.
Cu(NO3)2(aq) NaOH(aq) > Cu(OH)2(aq) NaNO3(aq)
Blue gelatinous copper(II) hydroxide forms
NaOH(aq) is mildly corrosive

3. Cu(OH)2(aq) + Heat --------> CuO(s) + H2O(g)
Cu(OH)2(aq) is not stable when heated and decomposes
Black CuO(s) is formed. React until no blue color is left
CuO(s) H2SO4(aq) > Cu(SO4)(aq) H2O(l)
Black CuO(s) is soluble in acid solution to form blue clear solution
6 M H2SO4(aq) is corrosive

4. Cu(SO4)aq + Zn(s) --------> Zn(SO4)aq + Cu(s)
Single replacement oxidation/reduction reaction gives us back copper
Must continue reaction until:
All blue color is gone from solution
All Zn(s) is dissolved. Excess Zn(s) will
C. Safety
1. HNO3 reaction in Hood (toxic NO2(g))
2. Add Zn in Hood. H2SO4 reaction with Zn gives flammable H2(g)
D. Techniques and Procedural Changes
1. Decant: pour off liquid; keep solid
2. Use 400 ml beaker, not 250 ml; sometimes more volume is needed
3. Final workup:
Decant liquid from beaker; transfer solid copper to
TARED evaporating dish
Wash with water; decant; wash with Methanol; decant; wash with Acetone, decant
Dry directly on hot plate.
E. %Yield = (Cu product mass)/(starting Cu mass) x 100%

5. Incident: NaOH Clothing Damage Incident: Acid Splash on Latex Gloves