Question

What is the net ionic equation of the reaction of $FeCl_2$ with $NaOH$ ? Express your answer as a chemical equation including phases.

Answer 1

To solve the given problem, we should have an understanding about Precipitate, Balancing an equation and solubility.Precipitate is the deposited substance formed after a reaction and is solid in nature.
To balance an equation, we have to add coefficients to the elaborated unbalanced form and make sure that the number of atoms are the same on each side. If a substance dissolves in a solvent, this ability is referred to as the solubility of the substance.

Complete step by step solution:
Step-1 :
First we should know that both are water soluble.
So, $FeCl_2 \leftrightarrow Fe^{ 2+ }(aq.) + 2Cl^-(aq.)$
$NaOH \leftrightarrow Na^+(aq.) + OH^-(aq.)$
Step-2 :
The balanced equation formed after mixing them are :
$FeCl_{ 2(aq.) } + 2NaOH \rightarrow 2NaCl_{ (aq.) } + Fe(OH)_2(s) \downarrow$
In the above reaction, $Fe(OH)_2$ is a ppt. formed by the mixing of $FeCl_2$ and $NaOH$ .
Step-3 :
The ionic equation for the balanced equation will be :
$Fe^{ 2+ }(aq.) + 2Cl^-(aq.) + 2Na^+(aq.) + 2OH^-(aq.)$
$\downarrow$
$2Na^+(aq.) + 2Cl^-(aq.) + Fe(OH)_2(s) \downarrow$
Removing $Na^+$ and $Cl^-$ from both side, we get ,
$Fe^{ 2+ } (aq.) + 2OH^-(aq.) \rightarrow Fe(OH)_2(s) \downarrow$

Additional Information:
When green coloured ferrous chloride solution reacts with sodium hydroxide solution to form green colour precipitate of ferrous hydroxide and colourless sodium chloride solution.

Note:
$FeCl_2$ is a soluble inorganic compound in water and $NaOH$ is a strong alkaline colourless solution. When $Fe(OH)_2$ is exposed to air, $Fe(OH)_3$ is formed which is reddish brown in colour.