According to the given formula list, formality is defined for an ionic solute as
A$\dfrac{\text{Wt. of ionic solute}}{\text{Formula wt. of solute} \times V_{in\,L}}$
B$\dfrac{\text{Moles of solute}}{\text{Volume in mL}}$
C$\dfrac{\text{Wt. of solvent}}{\text{Wt. of solution}} \times 100$
D$\text{Molarity} \times \text{Eq. wt.}$
Answer & Solution
Correct answer: A. $\dfrac{\text{Wt. of ionic solute}}{\text{Formula wt. of solute} \times V_{in\,L}}$
The page explicitly defines formality as $\dfrac{\text{Wt. of ionic solute}}{\text{Formula wt. of solute} \times V_{in\,L}}$. It is used especially for ionic compounds where the formula unit is a more natural basis than a discrete molecule.
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