Aqueous copper sulphate solution gives a green precipitate of A with aqueous potassium fluoride. What would be the correct molecular formula of A?
1. [CuF₆]^3–
2. [CuF₄]^2–
3. [CuF₂]^–
4. [CuF₅]^4–

The oxidation number and coordination number of Co in the complex K₃[Co(C₂O₄)₃] respectively are:

The coordination number and oxidation number of Co in the complex (NH₄)₂[CoF₄] are:
1. +2, 4
2. 4, +2
3. 6, +3
4. +3, 6

The correct IUPAC name of the complex K[Cr(H₂O)₂(C₂O₄)₂].3H₂O is:

1. Potassiumdiaquadioxalatochromate(III)trihydrate

2. Diaquadioxalatopotassiumchromate (III) trihydrate

3. Potassiumdihydridodioxalatochromate(IV)trihydrate

4. Potassiumdiaquadioxalatochromate(II)trihydrate

Number of ions produced from the complex [Co(NH₃)₆]Cl₂ in an aqueous solution are:

1. 6      

2. 4    

3. 3        

4. 2

The oxidation number of Cobalt in K[Co(CO)₄] is :

1. +1       

2. +3         

3. –1         

4. –3

The most stable complex among the following is:

1. [Fe(H₂O)₆]³⁺     

2. [Fe(NH₃)₆]³⁺       

3. [Fe(C₂O₄)₃]^3–       

4. [FeCl₆]^3–

${\mathrm{FeSO}}_4$ solution mixed with ${\left({\mathrm{NH}}_4\right)}_2{\mathrm{SO}}_4$ solution in 1:1 molar ratio gives the test of Fe²⁺ ion but ${\text{CuSO}}_4$ solution mixed with aqueous ammonia in 1:4 molar ratio does not give the test of Cu²⁺ ion because: