Lab Report Copper

Abstract:

Pure elemental copper was cycled through a series of five chemical reactions and changes in the physical properties of the solution (or precipitate) was observed. Using a variety of methods such as precipitation reactions, acid-base reactions, and oxidation-reduction (or redox) reactions, copper was converted and transformed into different states, including solid compounds and ionic form. After all the transformations, it was concluded that the percent recovery of copper was 126%, which was determined by calculating the mass copper remaining divided by the initial mass and multiplied by 100.

Introduction:

The purpose of this experiment was to observe various reactions including copper at different stages of the cycle and to identify

By cycling copper through a series of reactions, copper will be precipitated and at the end of the cycle, these observations are used to verify the Law of Conservation of Mass. Precipitation reactions are reactions in which a solid or precipitate forms when two solutions are mixed. It involves the combination of soluble cations and anions to form a solid, insoluble compound that precipitates. Acid-base reactions occur when an acid reacts with a base and the two neutralize each other to produce water and a salt. Oxidation-reduction (redox) reactions are reactions in which electrons transfer from one reactant to the other. Decomposition reactions is a reaction in which a compound breaks down into one or more elements or new compounds. Double displacement reactions are where the positive ions (cations) and the negative ions (anions) switch places to form new

Elemental copper with its elemental charge of 0 will transform to (Cu+2) when reacted with nitric acid, which is an oxidation-reduction (redox) reaction. In reaction two, once the copper has dissolved, 20 mL of 6.0 M NaOH was added to the beaker, while the solution is being stirred. The precipitation reaction is observed since (Cu+2) transform into solid copper (II) hydroxide Cu(OH)2 with sodium hydroxide (NaOH). In the third reaction, the beaker was heated on a hot plate until the solution begins to boil because at this point, the blue Cu(OH)2 has been converted to black CuO. When heated, Cu(OH)2 will decompose into copper (II) oxide and water, which is a decomposition reaction. In reaction four, 5 mL of 6.0 M H2SO4 (sulfuric acid) was added to the mixture and within minutes of stirring, all the black CuO dissolved. An acid-base metathesis and double displacement reactions were observed since copper is returned to a solution as an ion (Cu+2) when CuO is reacted with sulfuric acid. In reaction five, 1.0g of 30-mesh zinc was added to the solution and the supernatant was colorless (not blue). Remaining in the hood, 5 mL of distilled water followed by 10 mL of concentrated hydrochloric acid was added to remove excess zinc. Copper will then transform back to the elemental copper through an oxidation-reduction reaction because of