Copper Synthesis Experiment

Experiment 1: Synthesis of Copper Compounds

Introduction

This experiment involves the synthesis of compounds originating from pure solid copper. By applying solubility rules and the reactive properties of substances, many compounds which would otherwise be costly to extract from nature are able to be synthesized in the laboratory. Laboratory synthesized may sometimes be more economical than natural extraction, however it poses its own problems with the amount of substance that is actually yielded from the production reactions (Stathopulos, 2007). Almost no reaction has 100% yield, thus scientists inadvertently produce undesired products that must be filtered or decanted out of solution (Petrucci et al, 2007). Beginning with pure copper wire, this experiment will exhibit its transformation to substances including Cu(NO3)2, Cu(OH)2, CuO, CuSO4 . 5H2O and finally returning to pure copper (Cu). The experiment objective is to successfully complete these conversions and then calculate the percentage of recovered copper using the initial and final mass data obtained.

Procedure

Please refer to "Experiment 1: Synthesis of Copper Compounds" on pages 11-13 in the CHEM 120L lab manual for the procedure outline. All steps were followed without deviation.

Results and Observations

Please refer to the calculations and tables (16) located on the following 2 pages.

INITIAL MASS (copper wire) - 1.120g FINAL MASS (recovered copper - dish mass) - 37.88g

% Recovery = Recovered mass / Initial Mass . 100 = 37.88g / 1.120g . 100 = 3382%

Table 1- Reaction of Cu with Nitric Acid

Reaction Cu + 4HNO3  Cu(NO3)2 + 2NO2 + 2H2O

Description * Nitric acid dissolved copper wire completely

* A brown gas was produced

* Black precipitate formed

Table 2- Formation of Cu(OH)2

Reaction Cu(NO3)2 + 2NaOH  Cu(OH)2 + 2NaNO3

Description * Solution turned from a bright blue colour to a very dark blue

* Solution turned from very light to extremely thick, almost sludge like

Table 3- Conversion of Cu(OH)2 to CuO

Reaction Cu(OH)2 + heat  CuO + H2O

Description * Black precipitate formed while heating

* Lost 1 drop in transition to filter

* Filtrate was clear

* Sediment left on filter paper was black and clay-like

Table 4- Formation of CuSO4 from CuO

Reaction CuO + H2SO4  CuSO4 + 5H2O

Description * Black precipitate dissolved and solution turned blue with the addition of H2SO4

* Not all CuO dissolved

* Heat was required to dissolve additional CuO

Table 5- Formation of Cu metal from CuSO4

Reaction CuSO4 + Zn  Cu + ZnSO4

Description * Solid orange precipitate formed

* Clear/yellowish gas is produced

* Zinc dissolves

Table 6- Removal of excess Zn with acid

Reaction 2ZnSO4 + 2 HCl  2ZnCl + H¬¬2 + 2SO4

Description * No reaction occurred

* All excess zinc was used up

* Small amount of CuO residue

Discussion

What this lab mostly involved was the formation of new substances and combinations of copper using prior knowledge of reactivity and solubility rules. The intent of the experiment was to perform all the reactions only to return to the pure form of copper again. A reasonable percent recovery would be 90% +, however, the percent recovery obtained in our experiment was an outrageous and impossible figure of 3382%. Unless the law of conservation for matter is wrong, only error can explain that abnormal figure. Under the guidance of our TA, we were advised to remove our evaporating dish from the Bunsen burner to prevent overheating and the formation of copper oxide. A very reasonable claim, though in doing so it left much of the water un-evaporated accounting for much of the extra mass measured. The heat that was being applied was not intense heat, it was turned down to a rather low setting so that it would be hot enough to evaporate the water but not cause the copper to "pop" and end up all over the counter top. in addition, the copper was likely bunched up in the dish opposed to spread out which may also contribute to the lack of evaporation. The formation of copper oxide render the copper sample impure as it would have additional oxygen mass. Aside from the obvious mass error,