To gain familiarity with basic laboratory procedures, some chemistry of a typical transition element, and the concept of percent yield. Apparatus and Chemicals
|0.5 g piece of no. 16 or no. 18 copper wire |evaporating dish | |250 mL beaker (2) |weighing paper | |concentrated HNO3 (4 – 6 mL) |6.0 M H2SO4 (15 mL) | |graduated cylinder |granular zinc | |3.0 M NaOH (30 mL) |methanol | |carborundum boiling chips |acetone | |stirring rod |towel | |iron ring and ring stand |balance | |wire gauze |aluminum foil cut in 1-inch squares | |Bunsen burner |concentrated HCl (drops) |
Most chemical synthesis involves separation and purification of the desired product from unwanted side products. Some methods of separation, such as filtration, sedimentation, decantation, extraction, and sublimation were discussed earlier. This experiment is designed as a quantitative evaluation of your individual laboratory skills in carrying out some of these operations. At the same time you will become more acquainted with two fundamental types of chemical reactions -- redox reactions and metathesis (double-displacement) reactions. By means of these reactions, you will finally recover the copper sample with maximum efficiency. The chemical reactions involved are the following. Cu(s) + 4 HNO3(aq) -----> Cu(NO3)2(aq) + 2 NO2(g) + 2 H2O(l) Redox  Cu(NO3)2(aq) + 2 NaOH(aq) -----> Cu(OH)2(s) + 2 NaNO3(aq) Metathesis  Cu(OH)2(s) -----> CuO(s) + H2O(g) Dehydration  CuO(s) + H2SO4(aq) -----> CuSO4(aq) + H2O(l) Metathesis  CuSO4(aq) + Zn(s) -----> ZnSO4(aq) + Cu(s) Redox  Each of these reactions proceeds to completion. Metathesis reactions proceed to completion whenever one of the components is removed from the solution, such as in the formation of a gas or an insoluble precipitate (driving forces). This is the case for reaction , , and , where in reactions  and  a gas and in reaction  an insoluble precipitate are formed. Reaction  proceeds to completion because zinc has a lower ionization energy or oxidation potential that copper.
CHEMISTRY - NCHS Lab: Reactions of Copper and Percent Yield Page 1 of 8 The objective in this experiment is to recover all of the copper you begin with in analytically pure form. This is the test of your laboratory skills. The percent yield of the copper can be expressed as the ratio of the recovered weight to initial weight, multiplied by 100: [pic]
• Weight approximately 0.500 g of no. 16 or no. 18 copper wire (1) to the nearest 0.0001 g and place it in a 250 mL beaker. Add 4-5 mL of concentrated HNO3 to the beaker, IN THE HOOD. After the reaction is complete, add 100 mL distilled H2O. Describe the reaction (6) as to color change, evolution of gas, and change in temperature (exothermic or endothermic) in the report sheet. • Add 30 mL of 3.0 M NaOH to the solution in your beaker and describe the reaction (7). Add two or three boiling chips and carefully...