Nickel ion testing is done by identifying colours nickel metal compounds or forming precipitates or solutions with other reagents. Nickel metal is placed in 3d block and it's atomic number is 28.
In this tutorial, we study about followings.
Ni is the 22nd most abundant element in the earth's crust and occurs in a variety of sulfide ores. General configuration of nickel is 4s2 3d8. Major oxidation state of nickel is +2. Nickel is a silvery metal that has a beautiful high polish.
Nickel is soluble in dilute acids such as HCl or dilute H2SO4 to form green solution
hexaaquanickel(II) ion /
[Ni(H2O)6]2+ and hydrogen gas (H2).
Ni(s) + 6H2O(l) + 2H+(aq) → [Ni(H2O)6]2+(aq) + H2(g)
If an alkali, NaOH is added to this green solution, a green precipitate, [Ni(OH)2(H2O)4] is formed.
When we testing nickel ion and it's compounds we should have a knowledge of whether those compounds are precipitates or solutions and colours of them.
Add NH3(aq) solution to Ni2+(aq) solution. Nickel hydroxide, Ni(OH)2, a light green precipitate is formed. When add excess NH3(aq), Ni(OH)2 precipitate dissolve and give blue colour solution due to formation of [Ni(NH3)6] complex. If you add concentrated NH3(aq) solution, intensity of blue colour will be increased.
Send hydrogen sulfide (H2S) under acidic state to nickel(ii) ion solution. But a precipitate doesn't form.
Send H2S when NH3(aq)/NH4Cl are exist in nickel(ii) ion solution. Then you can see a Nickel sulfide (NiS) ,a black precipitate is formed. Also add (NH4)2S to nickel(ii) ion solution. It also gives NiS ,the black precipitate.
Ni2+(aq) ions reacts with concentrated Cl- ions in the presence of ethanol medium to give tetrachloronickel(II) ion / [NiCl4]2-, a blue solution.
Ni2+(aq) ions reacts with concentrated Cl- ions in the presence of acids to give
tetrachloronickel(II) ion / [NiCl4]2-, a yellow brown solution.
[NiCl4]2- is a tetrahedral complex.
Ni2+(aq) ions reacts slowly with nitrile ions (CN-) to give
nickel cyanide / [Ni(CN)2], which is a light green precipitate.
This precipitate will dissolve in excess CN- to form tetracynonickel(II) ion / [Ni(CN)4]2-, yellow colour solution.
Add dimethylglyoxime(DMG) to Ni2+ solution. Next add little bit of NH3(aq) to make solution basic. It will give a red precipitate.
This is a very specific testing reaction of nickel ion.
Nickel (+II) ion gives a green colour solution in aqueous state.3d metal ions compounds colours
Major oxidation state of nickel metal is +2.
Yes. Nickel is used as a catalyst in different applications.
Qualitative Analysis for anions and cations