Experiment 1: Reactions Of Copper Flashcards
This experiment produces a series of copper compounds from metallic copper:
Cu -> Cu(NO3)2 -> Cu(OH)2 -> CuO -> CuSO4 x 5H2O -> Cu
In this experiment:
- Initial copper is to be eventually recovered as metallic copper, isolated as a pure substance, and weighed
- To recover nearly all the copper as pure copper, try to prevent loss by avoiding spattering while boiling, leaving product on sides of beakers, and spilling of product.
- purify precipitates by washing efficiently and then drying appropriately before weighing
Percent yield
In this case, using the recovered mass of solid copper and the starting mass of the initial copper, use the equation:
% yield = actual yield (g) / theoretical yield (g) x 100
Purpose of using percent yield equation
- assesses the effectiveness of a reaction by looking at how much of the desired product is obtained from the reaction and ignores any unwanted side products — assuming that the recovered product is pure
Atom Economy
% AE = molar mass of desired product/molar masses of all reactants
- used to assess if a reaction meets green chemistry standards
Step 1 of the Experiment:
Converting copper metal to copper (II) nitrate
- Sand copper wire to remove surface contaminants
- exact mass of copper obtained
- using nitric acid to dissolve copper wire
- colour change, bubbling/fizzing, coloured gas produced
- green solution will be formed, the gas is trapped and needs to be swirled to obtain blue solution
Step 1 Experiment Reaction Equation
Cu (s) + 4 HNO3(aq) —> Cu(NO3)2(aq) + 2NO2(g) + 2H2O(l)
Step 2 of the Experiment:
Converting copper (II) nitrate to copper (II) hydroxide
- dilute solution with DI water — add water quickly
- baseify copper (II) nitrate solution sodium hydroxide
- slow addition of NaOH with stirring, temperature increases
- solution should be strongly alkaline (pH > 10)
Step 3 of the Experiment (Part 1):
Converting copper (II) hydroxide to copper (II) oxide
- heat copper (II) hydroxide gelatinous mixture with Bunsen burner
- stir to prevent bumping
- colour change will occur, black CuO
- thorough heating is required to form a particulate solid that is finely divided and easily filtered out of the aqueous solution
- the solid black CuO should separate from the clear liquid supernatant
Bumping definition
- Mixture needs to be heated slowly, if not, rapid heating can cause air bubbles to form underneath the solid that is being produced
- When the air bubbles pop, a great quantity of material will come out of the beaker
Step 3 of the Experiment (Part 2):
Isolation copper (II) oxide by filtration
- once solid CuO is produced, it needs to be isolated from the aqueous solution using vacuum filtration
- all copper must be recovered, discard filtrate into the appropriate waste container in the fume hood
Supernatant definition
Clear liquid free of precipitate that forms during the chemical process of precipitatation
Filtrate definition
The liquid that passed through the filter paper
Step 4 of the Experiment:
Converting copper (II) oxide to copper (II) sulphate
- using dilute sulphuric acid, CuO will be converted to Cu2SO4
- transfer CuO into the beaker that contains the dilute sulphuric acid
- blue solution will be obtained
Step 5 of the Experiment:
Converting copper (II) sulphate to metallic copper
- weighing zinc is not important because it is an excess reagent
- using the snorkel exhaust, add the zinc in small portions
- when the blue colour disappears, all the copper sulphate has been converted to copper and some of the zinc has reacted to form ZnSO4 (not present as a solid)
