Student 12PIB Chemistry

2/7/07Miner’s Luck: Using Silver nitrate and Copper to Get SilverObjective:The purpose of this experiment is to practice stoichiometry calculations using the copper-silver nitrate reaction.

Materials: 30cm bare copper wire ≈1.50 grams silver nitrate Medium sized test tube filled with distilled water approximately filled 2/3. 100mL beaker stopper with hole for test tube distilled water in container stir rod

Data & Results:

Quantitative data: silver nitrate and copper labComponent Mass (g)Copper Wire Initial mass

1.51

Copper Wire Final mass

1.49

Copper Wire Change in mass

-0.02

AgNO3 mass 1.53100mL beaker 66.32Silver crystal + beaker

67.08

Silver crystal 0.76

Qualitative data: silver nitrate and copper labDuring the reaction, the liquid changed color from clear to transparent blue. As this was happening shiny white crystals began to form on the copper wire. After the ten minutes ended, the wire was fuzzy from the crystals. It was difficult to remove some small amount of crystals that fell off of the wire at the bottom of the test tube. The silver was heavier than the water or solution. There were more crystals at the top of the wire; they almost touched the sides of the test tube. There was a dark spot at the top of the crystal formation. The wire was a more dull copper color where the crystals grew in comparison to the part that was not in the solution.

Calculations:2AgNO3(aq) + Cu(s) Cu(NO3)2(aq) + 2Ag(s)

1. 1.49g(final) -1.51g(initial) = -0.02g change in mass of copper2. s

0.02g Cu 1 mol Cu 2 mol Ag 107.87g Ag = 0.08g Ag63.65g Cu 1 mol Cu 1 mol Ag

3. 67.08g(silver + beaker)-66.32g(beaker)= 0.76g mass of silver4. 0.76gAgA/0.08gAgT= 22.42*100= 950% bad…5. AgNO3 mass = 1.53g6.

1.53g AgNO3 1 mol AgNO3 2 mol Ag 107.87g Ag = .972g Ag169.88g AgNO3 2 mol AgNO3 1 mol Ag

7. The answer to number two should have been greater than the amount of silver that

we collected. The answer that was lesser would have been the limiting reactant however my group probably made an error in massing the copper. The silver nitrate would have been the limiting reactant if the 1.51g of copper was allowed to completely react, but for the short amount of time that the copper was allowed to react, the copper was the limiting reactant. As I said before, we made an error in the massing of the copper wire that led to the bad calculations.

Conclusion & evaluation:Since this lab was a practice for stoichiometry, the main purpose was the equations. The data that I have collected was not good to create the proper equations. One of the errors that I assume happened was the massing of the wire. Somehow the change in mass was only 0.02g which was not possible with the 0.76g of silver we obtained. Perhaps we did not dry out the copper wire enough or made an error in the massing of the silver in the beaker; both would have caused the discrepancies. Also some copper might have been at the bottom of the test tube. For the massing of the Silver and the beaker, I massed the beaker alone and my partner massed the beaker with silver. I do not know if she used the same scale. There might have also been an error in verbal communication; we always verbally transmitted the masses to each other. The equations were set up correctly even though I end up with 950% yield. For future labs I will be sure to be more cautious in the massing of substances and I plan to watch out for these problems. Perhaps for future investigations of Stoichiometry we should do written problems not to have these errors. This will insure more accurate data. In order to redo this lab we could allow the copper to completely dissolve. This would eliminate the need for the second massing of the copper.