Molarity = moles / liter of solution
Given, Moles of Fe³⁺ = 0.200
Volume of solution = 725 ml = 0.725 L
Conversion factor: 1000 ml = 1L
Molarity = 0.200 / 0.725 L = 0.275 M
The dissociation of Fel₃ in water is ad follows:
Fel₃ → Fe³⁺ + 3l⁻
1 mole of Fel₃ gives 1 mole of Fe³⁺ ions and 3 moles of l⁻
Since the solution is 0.275 M of Fel₃, so there are 0.275 M of Fe³⁺ ions,
and (3 x 0.275 M) = 0.825 M of l⁻ ions.
You can measure length wiht the greatest preciaion using a tape measure marked in milimeters.
Answer: C. milimeters.
