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Chemistry

Essay by   •  November 13, 2010  •  1,506 Words (7 Pages)  •  1,296 Views

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Data/ Observations

Data:

* Measurements:

- Paper towel = 0.5100 g

- Cu + Paper towel = 1.1000 g

- HNO3 = 5.01 mL

- H2O = 100 mL

- NaOH = 30.001 mL

- Wax Plate = 2.291 g

- Zn + Wax Plate = 4.693 g

- Zn = 2.402 g

- Methanol = 5.19 mL

- Acetone = 5.30 mL

- End Product Cu + Wax Plate = 2.970 g

- End Product Cu = 0.679 g

Observations:

* The copper at the beginning was a light reddish and powdery solid.

* When the HNO3 was added, the liquid turned green and produced an orange gas (NO2 (g)). There was a grainy substance on the bottom. There was no change in temperature.

* When the NO2 was gone, the solution still smoked.

* When we added the water, the solution went from a green to a very crystal, pretty blue. The substance stopped smoking and the grainy substance at the bottom went away, it dissolved. There was no change in temperature.

* After the NaOH was added, the solution turned a more vibrant and bright blue and had almost a jelly look to it. The jelly looked sort of like the lava in lava lamps because it was in small liquid/solid balls smooshed together.

* When the blue, jelly substance stayed out for a while, it turned a little whitish at the top. Still no change in temperature.

* When the substance began to boil, it turned very black and grainy. The liquid was separate than the solid. It looked like dirt on the bottom of a lake or some body of water.

* After we added the H2SO4, the liquid turned light blue again and the solids now float to the top. There did not seem to be as much solid as there was before.

* When we added the Zn, the liquid turned brown and it sort of looked like hot chocolate. The "dirt" looking solid and the extra zinc stayed on the bottom of the beaker. The excess zinc kept bubbling, until it finally went away all together. This reaction actually changed in temperature. The beaker was very warm after it all denoting that the reaction was exothermic.

* The last product of copper was a dark reddish brown and it still looks powdery and like dirt. It is much darker than the copper we used in the beginning of the experiment.

Calculations/ Results

* (We kept having to add more Zn to our solution because it had a bluish tint. This is the sum of the amount of Zn we had to put in it.)

4.291 g Zn and Wax Plate + 0.134 g Zn + 0.134 g Zn + 0.134 g Zn =

4.693 g Zn and Wax Plate

* (Zn + Wax Plate (g)) -Wax Plate (g) = Zn (g)

4.693 g - 2.291 = 2.402 g Zn

* (End Cu + Wax Plate (g)) - Wax Plate (g) = End Cu (g)

2.970 g - 2.291 g = 0.679 g Cu

* Percent Yield = Experimental Value x 100%

Theoretical Value

0.679 g Cu x 100% = 135.8 % yield

0.500 g Cu

Conclusions:

In this experiment, the goal was to recover all of the copper, in the end of the experiment, that we initially began with and to also calculate the percent yield. First of all, we measured out 0.500 g of copper(Cu) and put it in a beaker. Then, in the hood, we added about 5.00 mL of HNO3. The solution, the liquid turned green and there was grainy solid on the bottom of the beaker (Cu(NO3)2(aq) and H2O(l)), and it also produced an orange gas (NO2 (g)) along with a white wispy smoke after the NO2(g) was gone. When that reaction was complete, we then added 100 mL of H2O. The liquid went from green to a light blue and the solid at the bottom disappeared. There was no change in temperature in either of those reactions.

Next, we added 30.001 mL of 3.0 M NaOH, which caused the solution to look like a lava lamp almost. Everything turned a vibrant, bright blue where there was the liquid (NaNO3(aq)), and also a "lava" looking solid (Cu(OH)2(s)) which was in little ball shapes and smooshed together. We then added about 2 or 3 boiling chips into the solution and then we heated it up while stirring. When we finally reached the boiling point, the solution had turned black and it had little "specs of dirt" floating around. After the solution sat out for a while, the solids (CuO(s)) and the liquid (H2O(l)) separated with the water on top of the copper (II) oxide. Then we decanted the solution so that only the copper (II) oxide

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