Question

Oxalate ion will interfere with the Group D tests after we make the solution acidic. Also, ammonium ion may prevent the precipitation of Group Dcations as hydroxides in sodium hydroxide solution. Thus, must treat the supernatant liquid left after we have precipitated calcium oxalate, in order to destroy any remaining Oxalate or ammonium ions prior to further analysis. To accomplish this, we transfer the solution to a crucible, add concentrated nitric acid and heat the mixture to dryness in a fume hood. This treatment produces solid black copper (1) oxide and white potassium hydroxide. Adding solution dissolves the two solids making aqueous green tetrachlorocuprate (II) and aqueous potassium ions. What is the formula for tetrachlorocuprate (l? With the oxalate and ammonium removed the tetrachlorocuprate (ll) and the potassium ion can be separated by adding 6M sodium hydroxide to the mixture until it is neutral. Then add 1M sodium hydroxide to precipitate copper () hydroxide, while the potassium is aqueous. Balance the equation + () OH)ls, blue)+ chael Next heat the mixture in boiling water bath to promote conversion of the insoluble blue copper (1) hydroxide into copper (II)oxide and water. Write the reaction with phases. Alter decanting the supernatant liquid containing potassium ion from the solid copper (il oxide, dissolve the solid with making the tetrachlorocuprate (II)ion Verifying the presence of copper requires the pH to be adjusted to 4-5 and adding KLEICN). The precipitation of maroon copper hexacyanaferrate (11), or copper (11) ferrocyanide, CuECN shown below verified coppers presence Balance the equation Cucullea, reen+ Fe(CN):d* (sa yellow) Fe(CN): (s, maroon + prael

Answer 1

Formula of tetrachlorocuprate(II) = [CuCl₄]^2-

Balanced equation :

[CuCl₄]^2-(aq) + 2 OH^-(aq) $\leftrightarrow$ Cu(OH)₂(s, blue) + 4 Cl^-(aq)

Balanced equation :

Cu(OH)₂(s) $\rightarrow$ CuO(s) + H₂O(g)

Balanced equation :

2 [CuCl₄]^2-(aq, green) + [Fe(CN)₆]^4-(aq, yellow) $\leftrightarrow$ Cu₂Fe(CN)₆(s,maroon) + 8 Cl^-(aq)