1. Calculate the theoretical yields of the compounds to be prepared in this expe
ID: 796163 • Letter: 1
Question
1. Calculate the theoretical yields of the compounds to be prepared in this experiment. The metal ion in both cases is the limiting reagent. Hint: Find the number of moles of Cu(II) in the sample of CuSO4 5H20 that you used. That will equal the number of miles of [Cu(NH3)4] SO4 H20 that could theoretically be prepared. Proceed in a similar way for the synthesis involving Co(II).
a.
b.
2. How could you establish that the metal ion is the limiting reagent?
3. How would you formally name the compound [Cu(NH3)4] SO4 H20 prepared in part a?
Explanation / Answer
Equipment and Supplies
Procedure
Please read the entire procedure before beginning this experiment
WEAR YOUR GOGGLES FOR THIS EXPERIMENT
1. Weigh out 7.0 g of CuSO4 5H2O on an analytical balance. Weigh the solid either on a piece of paper or in a small beaker and not directly on the balance pan. Record the exact mass.
2. Transfer the solid copper sulfate to a 125 mL Erlenmeyer flask and add 15 mL of distilled water. Heat the flask to dissolve the solid, then cool to room temperature.
3. Carry out the remaining steps under the hood. Add 15 M NH3 solution, a few mL at a time, swirling the flask to mix the reagents, until the first precipitate has completely dissolved. All the copper should now be present in solution as the complex ion Cu(NH3)4+2. CAUTION: concentrated ammonia is extremely caustic. Avoid getting it on your skin or breathing the vapors.
4. You can precipitate the sulfate salt of this complex cation by adding a liquid, such as ethyl alcohol, in which Cu(NH3)4S04 H2O is insoluble. Add 10 mL of 95% ethyl alcohol to the solution; this should form a deep blue precipitate of Cu(NH3)4S04 H2O.
5. Filter the solution through a Buchner funnel, using suction. Wash the solid in the funnel by adding two 5 mL portions of 95% ethanol.
6. Dry the solid by pressing it between two pieces of filter paper. Put the crystals on a piece of weighed filter paper and let them dry further in the air.
7. When the crystals are thoroughly dry, weigh them on the paper to 0.001 g. Record the exact mass. Use this to calculate the percent theoretical yield.
8. Dissolve a small portion (about 0.5 g) of the complex ion, [Cu(NH3)4] SO4 H2O, in a few mL of water. Note the color and observe the effect of adding a few drops of 12 M HCl. When you complete Part B, show your product to your instructor for evaluation. CAUTION: concentrated hydrochloric acid is extremely caustic. Avoid getting it on your skin or breathing the vapors.
Copper sulfate pentahydrate (CuSO45H2O) Weighing paper 15 M Ammonia (NH3) Filter paper 125 mL Erlenmeyer flask Ringstand and ring 95% Ethanol Side-arm flask Balance Bunsen burner Buchner funnel 250 mL BeakerRelated Questions
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