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

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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

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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.

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http://www.youtube.com/watch?v=dExpJAECSL8

Copper

Chemical element with the symbol CuAtomic number 29 Good electrical and thermal conductorPure copper is soft and malleableAn exposed surface has a reddish-orange tarnishIt is used as a conductor of heat and electricity, a building material, and a constituent of various metal alloys

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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.

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The copper cycle

The cycle of copper reactions to be performed in this experiment

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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 variouselements 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!

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Reaction 2: Converting copper nitrate to copper hydroxide

Cu(NO3)2(aq) + 2NaOH(aq) Cu(OH)2(s) + 2NaNO3(aq)

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Reaction 3: Converting copper hydroxide to copper oxide

Cu(OH)2(s) + heat CuO(s) + H2O(l)

Dehydration involves the loss of water

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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.

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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.

After this point the solid, pure copper can be isolated, dried and weighed.

Hydrogen gas is highly flammable and will burn in air at a very wide range of concentrations between 4% and 75% by volume.

http://en.wikipedia.org/wiki/Hydrogen 11

Zn(s) + HCl (aq) ZnCl(aq) + H2(g)

Weigh and calculate the mass of copper recovered and your percent yield using the following equation:

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· 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.

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· 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.

Safety Notes

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