The Synthesis of Cuprous Chloride The chemical and physical properties of Copper

Question

The Synthesis of Cuprous Chloride The chemical and physical properties of Copper, like those of the other Transition Metals, are heavily influenced by the presence of d-subshell electrons in its outer orbitals. However, Copper forms an exception to the general Aufbau electron filling scheme in that its energy than its 4s orbital, resulting in an electron configuration of 3d orbitals are lower in This is consistent with Copper's placement in Group 1B of the Periodic Table of the Elements, suggesting it has but a Copper, Silver and Gold placed within the same chemical group as the Group 1 Na, K, Rb, Cs). This electron configuration suggests ionically bonded salts of Copper should involve Cu tons, where the outer 4s electron is lost Cu+·-[M 3do and, this is frequently the case. Salts of Cu are reasonably common, often water insoluble and mostly white in color. However, Cu is readily oxidized to Cu in most aqueous solution conditions. So, Cu salts are much more common than the Cu" salts; many of these salts are water soluble and highly colored single valence electron. In fact, Mendeleev's original Periodic Table had In this exercise we will convert elemental Copper into the salt Cuprous Chloride, in which the per is in the less common Cu state. Thisis somewhat tricky because of the tendency of the Cu" ion to oxidize to Cu. Our approach will be to first Oxidize the metalic Copper into one of Chloride (CuCh) compound. In general, the oxidation process strips electrons away and Reduction adds them. The specific chemical reactions to be carried-out are Cu(NO3)2(ap + 2 Noag) + 2H2O(Eq.3) Cu(s) + 4 HNOxaq) + where the Cupric Nitrate exists as: such that the Cupric lon can be precipitated as the Carbonate sale Cu2+(aq) + CO32-(aq) - CuCOy(s) E4. 5 2 Eq. 6) 2 CuC14 (aq) 2- Eq. 8) CuCl(s) 3 Cl (aq) + CuCls (ag)

Explanation / Answer

Procedure:

1. Obtain a 1 g of the sample of copper metal. weigh the sample on the analytical balance.

2. in a fume hood, put the metal in a 150 mL beaker and add 5 mL of 15 M HNO3 (Use concentrated stock solution it gives 15 M solution). a blue solution of cupric nitrate Cu(NO3)2 will be produced. if necessary you may gently warm the solution.

Cu(s) + 4 HNO3 = Cu(NO3 )2 + 2 NO2 + 2 H2O

3. when all the copper is dissolved add 50 mL of water and allow the solution to cool. Be sure that no more fumes of NO2 are present before you proceed to the next step.

4. Weigh out 5 g of sodium carbonate, Na2CO3. add small amount of sodium carbonate to the solution, adding the solid as necessary when the evolution of CO2 subsides. Stir the solution well after each addition. when the acid is neutralized a blue-green precipitate of CuCO3 will begin to form. At this point, add the rest of the Na2CO3, stirring the mixture well to ensure complete precipitation of the copper carbonate. the following chemical reaction is taking place

Cu2+ (aq) + CO32- (aq) = CuCO3 (s)

5. filter the precipitate using Buchner Funnel. Use your Rubber policeman and spray from your wash bottle to make a complete transfer of solid. wash the solid well with distilled water.

6. transfer the solid to a 150mL beaker. add 10 mL of water. then slowly add 30ml of 6M HCl, stirring continuously. the following chemical reaction is taking place

CuCO3 (s) +2H+ (aq) + 4Cl- (aq) = CuCl42- (aq) + CO2 (g) + H2O

7. When all teh solid has dissolved add 1.5 g of copper turnings and cover the beaker with watch glass. Place on a hot plate in the fume hood.

8/ Heat the mixture to boiling point and keep it at that temperature, just simmering for 30 min. It may be that the dark coloured solution that forms will clear to a yellow colour before that time is up, and if it does, you may stop heating and proceed with the next step.

CuCl42- (aq) + Cu (s) + 4Cl- (aq) = 2CuCl43- (aq)

9. while the mixture is heating put 150 mL distilled water in a 400 mL beaker and put the beaker in an ice-bath. cover the beaker with a watch glass

10. After you are heating the Cu-CuCl2 mixture, carefully decant the hot liquid into the beaker of chilled water, taking care not to transfer any of the excess Cu metal into the beaker white crystals of CuCl should form. Continue to cool the beaker in the ice bath to promote crystallization and to increase the yield of solid

11. Cool 25 mL distilled water, to which you have added 5 drops of 6M HCl, in an ice bath

12. Put 20 mL acetone in a small beaker

13. Filter the crystal of CuCl in Buchner filter. Swirl the beaker to aid in transferring the solid to the funnel. just as the last of the liquid is being pulled through wash the CuCl with 1/3 fo acidified the cold water. Rinse the last of the cuCl into the funnel with another portion of the water and use the final 1/3 to rewash the solid. turn of the suction and ad 1/2 of the acetone to the funnel; wait about 10 sec. and turn the suction. Repeat this operation with the other half of the acetone. Draw air through the sample for a few min to dry it. If the solid has been properly washed, it will be pure white. if the moist compound is allowed to come into contact with air it will tend to turn pale green, due to oxidation of Cu+ to Cu2+

14. weight the cuCl , and label as follows

Name

Name fo the compound

Formula of the compound

Date

the weight of the product

question 4

1 g of copper contains 1/63= o.o15 moles as we know mole = weight/ molecular weight

now 1 M of copper react with 4 M of HNO3 so the mole s of HNO3 required = 0.015* 4= 0.6 M

excess HNO3 is used because cu is a unreactive metal adn doesn't react in normal circumstances with dilute acids. nitric acid is an oxidizing agent and the reaction is not the usela acid + metal reaction . the products are oxidies of nitrogen instead of hydrogen. the actual nitrogen oxide formed depends on the concentration and temperature of the acid

moles of sodium carbonate in 5 g , Mole = weight / molecular weight

= 5/105

0.047 M

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