<u>Answer:</u> The net ionic equation is written below.
<u>Explanation:</u>
Net ionic equation of any reaction does not include any spectator ions.
Spectator ions are defined as the ions which does not get involved in a chemical equation. They are found on both the sides of the chemical reaction when it is present in ionic form.
The chemical equation for the reaction of sodium carbonate and nickel (II) chloride is given as:

Ionic form of the above equation follows:

As, sodium and chloride ions are present on both the sides of the reaction. Thus, it will not be present in the net ionic equation and are spectator ions.
The net ionic equation for the above reaction follows:

Hence, the net ionic equation is written above.
A standard solution is a solution (in this case sodium hydroxide) whose concentration (molarity) is known very precisely. <span>The molarity of the sodium hydroxide solution cannot be determined accurately because s</span>olid sodium hydroxide is highly hygroscopic (absorbs water from the air) and cannot be accurately weighed. Sodium hydroxide form sodium carbonate because it absorbs carbon
dioxide from the air.