Question

STEPS:

Part III – Copper Charge

18. Measure and record the mass of a clean, dry crucible with its cover. Record this value to within 0.001 g.

19. Obtain and record the copper chloride hydrate mass.

a. Obtain about one gram (1 ± 0.1 g) of the unknown copper chloride hydrate using a weigh paper.

b. Place the unknown copper chloride in the crucible. Use a spatula to carefully break up any large pieces of the substance by pressing the pieces against the wall of the crucible.

c. Measure and record the mass of the crucible with the compound. Record your data to within 0.001 g.

20. Hold the burner in your hand and move the flame slowly back and forth underneath the crucible to gently heat the sample. Do not overheat the compound! The sample will make a popping noise and stick to the bottom of the crucible if overheated. Record anything that is observed during heating.

21. Once heating is completed, turn off the equipment and allow the sample to cool.

22. Remove the crucible cover and carefully inspect the sample. If any of the sample has maintained its initial appearance, reheat the sample until all of it has reacted.

23. Measure and record the mass of the cool crucible, lid, and dry (anhydrous) copper chloride sample. Record this mass to within 0.001g

24. Generate a solution of the copper chloride.

a. Transfer the brown solid to a clean and empty 50 mL beaker. Rinse out the crucible with two 8 mL aliquots (measured portions of a liquid) of deionized water and pour the water into the 50 mL beaker.

b. Gently swirl the beaker or stir the solution with a glass stir rod to completely dissolve the solid. Record any observations, particularly color change.

25. React the copper chloride solution to generate elemental copper.

a. Obtain a piece of aluminum wire. If the wire is dull, sand it with the sandpaper until shiny.

b. Coil the wire loosely around your index and middle fingers. Fewer coils are better.

c. Place the wire in the beaker of copper chloride solution so that it is completely immersed. It may need to be pushed down with a stir rod. Make sure the reaction goes to completion before continuing.

26. Complete the reaction.

a. Add 5 drops of 6 M HCl solution to dissolve any aluminum salts in the mixture, leaving a clear solution.

b. Use a glass stir rod to scrape off the copper from the aluminum wire into the beaker. Remove the aluminum wire from the solution and rinse it with deionized water or 1-2 drops of HCl to remove any additional copper.

c. Once the aluminum wire is rinsed, place the wire aside on a Kimwipe.

27. Collect and wash the copper produced in the reaction.

a. Set up a Büchner funnel for vacuum filtration.

b. Isolate the copper with the filter and rinse it with some deionized water.

c. Break up any large pieces of copper and rinse it twice with small amounts of deionized water.

d. Turn off the suction on the vacuum filtration apparatus.

a. Measure and record the mass of a clean, dry watch glass. Record this mass to within 0.001 g.

b. Remove the filter from the Büchner funnel and transfer the copper to the watch glass. Try to disperse the copper evenly on the watch glass.

c. Dry the watch glass with copper in an oven for 10-15 minutes.

d. Remove the watch glass using crucible tongs and let the watch glass cool.

e. When it is cool enough to touch, measure the mass of the watch glass and copper. Record this mass to within 0.001 g.

28. Dry the copper sample and take mass measurements.

29. Repeat drying in the oven and weighing the copper until the last two mass measurements are within 0.005 g of each other.

1. From the mass of copper measured in Part III, determine the moles of Cu.

Mass of crucible with cover was 37.111 g. Mass of copper chloride hydrate 38.066g total (0.958g of copper chloride hydrate). Mass of (anhydrous) copper chloride sample 37.857g (w/ crucible). Dry copper mass with watch glass (recorded 3 times after putting back in the oven) is 37.195g, 37.189g and 37.188g. The weight of the watch glass was 36.828g.

2. Determine the mass of chlorine in the original sample as the difference in mass between the anhydrous sample (after drying in the crucible) and the mass of copper. From the mass of chlorine, determine the moles of Cl.

3. Determine the experimental molar ratio of Cu:Cl.

4. In Step 26, describe the components involved in the reaction. What evidence is there for a chemical reaction? Describe where the reaction is occurring on the molecular level.

26) Complete the reaction.

a. Add 5 drops of 6 M HCl solution to dissolve any aluminum salts in the mixture, leaving a clear solution.

b. Use a glass stir rod to scrape off the copper from the aluminum wire into the beaker. Remove the aluminum wire from the solution and rinse it with deionized water or 1-2 drops of HCl to remove any additional copper.

c. Once the aluminum wire is rinsed, place the wire aside on a Kimwipe.

5)

a. Without attempting to measure the mass of the aluminum wire, consider the reaction that occurs in step 26, what would an increase in the metal wire mass indicate?

b. What would a decrease in the metal wire mass indicate?

Answer 1