Subsequent heating of the copper(II) hydroxide results in decomposition to copper(II) oxide and water.

The CuO can be quantitatively filtered, dried and weighed. The overall reaction for the sequence is:

MATERIALS NEEDED:
Safety goggles		100-ml beaker
Ring stand		Watch glass
Small iron ring		Balance
Large iron ring with wire gauze		Weighing dish
Bunsen burner		Drying oven or light
Beaker tongs		10-ml graduated cylinder
Filtering funnel		Rinse bottle with deionized water
Whatman #1 filter paper		1.8 to 2.2 grams CuSO45H2O
250-ml beaker		*10 ml of 6.0 M NaOH solution

* For 100 ml of a 6.0 Molar solution of NaOH, Using a 100-ml volumetric flask, dissolve 24.00 g of NaOH in about 50 ml of distilled water. Add distilled water carefully to a total volume of 100 ml. For 250 ml of 6.0 M NaOH, using a 250-ml volumetric flask, dissolve 60.00 g of NaOH into about 150 ml of distilled water. Add distilled water carefully to a total volume of 250 ml.

PRE-LAB:

1. Calculate the formula weight of both copper(II) pentahydrate and copper(II) oxide. Record on your DATA TABLE.

PROCEDURE:

2. Weigh between 1.8 and 2.2 grams of copper(II) sulfate pentahydrate in a weighing dish, to the nearest 0.01 gram. Be sure to use proper procedure for the balance used. Record the mass of the copper(II) pentahydrate on your DATA TABLE.

3. Transfer the chemical to your 250-ml beaker. Add 10 ml of distilled water to the beaker. Remember, use some of the water to rinse any chemical that remains on the weighing dish. This is quantitative so you need to make sure everything gets transferred. Swirl the beaker to dissolve the solid.

4. Add 10 ml of 6.0M NaOH to the solution in the beaker, and carefully swirl to mix. REMEMBER: 6M NaOH is very caustic, and will burn your skin.

5. Set up the ring stand and wire gauze. Place the beaker on the wire gauze, and set a watch glass over the beaker to cover. Heat the mixture to the boiling point. Try to avoid spattering especially on the watch glass. If spattering occurs use a wash bottle to wash all the solid back down into the solution. Heat until all the blue solid has been decomposed to copper(II) oxide and water (a few minutes). Allow the mixture to cool before filtering.

6. Fold a piece of Whitman #1 filter paper as shown in the drawing. Fold in half, then in fourths. Tearing off the outside corner, will make the filtering go faster.

7. Place the filter paper (after the corner is torn off) in the 100-ml beaker. If more than one person or group is conducting this experiment, mark your 100-ml beaker, with a pencil only, on the white square. Find the mass of the 100-ml beaker and filter paper to the nearest 0.01 g and record on your data table.

8. Open the cone with one thickness on one side, and three thicknesses on the other. Set-up a filtering funnel on the ring stand and small ring. Place the 100-ml beaker that you massed, under the funnel. While holding the filter paper in place, use your rinse bottle to wet the paper. This will seal it to the funnel.

9. Now transfer the previously heated mixture to the filter. Be careful to never allow the filter paper to be filled more than about 0.5 cm from the top of the paper. Be patient and add small amounts. when all the liquid has been transferred to the funnel, use your rinse bottle and with small amounts of water, wash all the solid precipitate into the filter paper.

10. When all the liquid has filtered through the filter paper, wash the precipitate, to remove any remaining sodium sulfate or sodium hydroxide. Use your rinse bottle, and rinse from the top of the filter paper down. Do 3 small rinses.

11. Discard the contents of the 100-ml beaker, and rinse it thoroughly with 4 or 5 rinses of distilled water from your wash bottle. Now carefully remove the filter paper containing the copper(II) oxide precipitate, and place it into the 100-ml beaker.

12. Place the beaker with the filter paper and precipitate in the drying oven at 105 ^oC, or under the drying light. Allow to dry for 24 hours.

13. After 24 hours. Remove the beaker containing the filter paper and precipitate from the drying oven and allow to cool.

14. When cool, find the mass of the beaker, filter paper, and precipitate to the nearest 0.01 g, and record in your DATA TABLE.

DATA TABLE:

Formula weight of CuSO₄5 H₂O = ____________

Formula weight of CuO = ____________

Mass of CuSO₄5 H₂O = __________ g

Mass of 100-ml beaker and filter paper = __________ g

Mass of 100-ml beaker, filter paper, and CuO precipitate = __________ g

CALCULATIONS:

15. Calculate the theoretical yield of CuO. This is calculated from the mass of CuSO₄5 H₂O used, and its relationship to CuO in the balanced equation. The formula would then be:

Theoretical yield of CuO = _________ g

16. Calculate the mass of CuO you obtained in the experiment (experimental yield). This is simply:

Experimental yield of CuO = _________ g

17. Now calculate the percent yield of CuO. The formula for this is:

Percent yield of CuO = _________ %

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