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Fe³⁺

Explanation:

When Fe²⁺ loses an electron, it becomes an Fe³⁺ ion.

   The loss of an electron in an atom makes the atom becomes positively charged. Further losing electrons makes the atom more positive.

 For the given ion;

 Fe²⁺   if it loses an electron more, it becomes Fe³⁺.

The expression is given as:

         Fe²⁺    →    Fe³⁺  +  e⁻

the electrical  conductivity  of asolution  of an electrolyte is measured by determining the resistance of thesolution  between two flat or cylindrical electrodes separated by a fixed distance.