Topic 15 Flashcards
What colour is an aqueous solution of cobalt hexaaquacolbat(II) ion. What structure does it assume?¡
Pink, octahedral.
What happens when aqueous cobalt (II) reacts with OH-. What happens to this product in the presence of excess NaOH?
Forms a blue/pink precipitate. [Co(OH)2(H2O)4] solid. Some redissolves in the presence of excess NaOH.
What happens when aqueous cobalt (II) reacts with ammonia. State any further reactions that may occur with excess ammonia.
Hexaaqua ion precipitates a hydroxide with NH3 which has a pink/blue colour. [Co(OH)2(H2O)4] is the precipitate. In excess ammonia, ammonia substitutes as a ligand: [Co(NH3)6] 2+ which is yellow/brown. But the ammonia ligands make this unstable and air will oxidise the Co+2 to Co +3 which is red/brown.
What happens when the hexaaquacobalt(II) reacts with carbonate ions. Can Co+3 go through this same reaction?
Co+2 reacting with carbonate ions forms CoCO3 precipitate which is mauve in colour. Co+3 cannot go through this same type of reaction.
What happens when hexaaquacobalt(II) reacts with Cl-, what shape does the product assume? How can you reverse this reaction?
The product is [CoCl4]2- blue solution. It assumes a tetrahedral shape and adding excess water reverses the reaction.
What colour is the aqueous copper(II)? What shape does it assume?
Blue solution and octahedral shape.
What happens when hexaaquacopper(II) ion reacts with NaOH. Is the product soluble in excess NaOH.
Form a pale blue precipitate of [Cu(OH)2(H2O)4]. It’s insoluble in excess NaOH.
What happens when the hexaaquacopper(II) ion reacts with a carbonate ion?
Forms a blue precipitate of CuCO3.
What happens when the hexaaquacopper(II) ion reacts with some ammonia? What happens when this product is reacted further with excess ammonia?
When reacted with some ammonia, it forms a blue precipitate: [Cu(OH)2(H2O)4]. When reacted with excess ammonia, it forms a royal blue solution: [Cu(NH3)4(H2O)2]2+.
What happens when the hexaaquacopper(II) reacts with Cl-? What shape does the product assume and how can we reverse the reaction?
You form the yellow [CuCl4]2- solution which is tetrahedral. Adding excess water reverses the reaction.
What happens when Cu+2 reacts with iodine ions? What type of reaction is this?
You form CuI. It is an off white precipitate. It takes part in a redox reaction.
Why is Cu+1 chemistry very limited? Describe which complexes it can form when it’s stabilised.
The Cu+1 species takes part in a disproportionating reaction where it’s positive Ecell value shows that it’s instantaneously reduced and oxidised. It’s rarely found in the Cu+1 form hence its chemistry is limited. It forms the stable [Cu(NH3)2]+ ion and stable [Cu(CN)2]- ion.
What are some uses of copper?
Some uses of copper include alloys like brass and bronze.
What colour is the hexaaquairon(II) ion?
Pale green
What is made when hexaaquairon(II) is added to OH- ions. Does it redissolve in very concentrated OH-? What further reaction occurs after this?
A dirt green precipitate of [Fe(OH)2(H2O)4] is made. It redissolves on very concentrated OH-. On standing in air it slowly turns a rusty brown due to oxidation to iron(III): [Fe(OH)3(H2O)]. Increasing the pH renders the Fe+2 unstable.
What happens when hexaaquairon(II) reacts with carbonate ions?
You form an off white precipitate of FeCO3.
