Test Nickel ion | Ni Metal Reactions, Ni2+

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.

  • Some reactions and characteristics of nickel metal - we study these things before testing Ni2+ ion because they are important in understanding Ni2+ testing experiments.
  • Test for chromium ion

Nickel metal

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.


Properties of nickel metal

  • Nickel react with dilute acids to form hydrogen gas and Ni2+ ion.
  • Nickel is a silvery white metal
  • No reaction between nickel and moisture in air
  • Powdered nickel readily reacts with carbon monoxide(CO) at normal conditions to form tetracarbonylnickel(0) ( [Ni(CO)4] ) complex. In this complex, oxidation number of Ni is zero.
    Ni(s) + 4CO(g) → [Ni(CO)4](g)


Reactions of nickel metal


Nickel and acids reaction

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. nickel metal and acid reaction



Testing nickel ion and compounds

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.


Nickel ion and aqueous ammonia solution | Ni2+ + NH3

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.

nickel ion and ammonia solution

Hydrogen sulfide and nickel(ii) ion | H2S + Ni2+

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.

nickel ion and ammonia solution


Nickel ion and chloride ion

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.

Nickel ion and chloride ion


Nickel ion and nitrile ions

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.

Nickel ion and nitrile ions


Nickel dimethylglyoxime complex test

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 dimethylglyoxime complex


Quetions


What are the precipitates of nickel ion?

  • Nickel hydroxide - Ni(OH)2
  • Nickel carbonate - NiCO3
  • Nickel cyanide - Ni(CN)2
  • Nickel sulfide - NiS
Metal precipitates and colours

What is the colour of nickel ion in aqueous state?

Nickel (+II) ion gives a green colour solution in aqueous state.

3d metal ions compounds colours

What ions nickel metal form?

Major oxidation state of nickel metal is +2.



Is nickel metal a catalyst? If it is give examples.

Yes. Nickel is used as a catalyst in different applications.