1
You visited us 1 times! Enjoying our articles? Unlock Full Access!
Question

# What is formality? Explain with example.

Open in App
Solution

## Formality:“It is defined as the number of gram formula mass of solute dissolved in per litre of solution.” It is used for ionic compounds.The formality of the solution is denoted by the symbol, $\mathrm{F}$.It is similar to normality.Formula used to calculate the formality:$\text{Formality}=\frac{\text{Number of gram formula mass of solute}}{\text{Volume of solution in litre}}$Or,$\text{Formality}=\frac{\text{Moles of solute}}{\text{Volume of solution in litre}}$Or,$\text{Formality}=\frac{\text{Given weight of solute}}{\text{Molecular weight of solute}×\text{Volume of solution in litre}}$For example:Calculate the formality of sodium chloride $\left(\mathrm{NaCl}\right)$ solution, $5.85\mathrm{g}$ of which have been dissolved to form $250\mathrm{mL}$ of the given solution.Step 1: Given,Weight of solute $\left(\mathrm{NaCl}\right)=5.85\mathrm{g}$Molecular weight of solute $\left(\mathrm{NaCl}\right)=58.5\mathrm{g}{\mathrm{mol}}^{-1}$Volume of solution $=250\mathrm{mL}=0.250\mathrm{L}\left(\because 1\mathrm{L}=1000\mathrm{ml}\right)$Step 2: To determine the formality of $\mathrm{NaCl}$ solution.$\text{Formality}=\frac{\text{Given weight of solute}}{\text{Molecular weight of solute}×\text{Volume of solution in litre}}$$\text{Formality}=\frac{5.85\mathrm{g}}{58.5\mathrm{g}{\mathrm{mol}}^{-1}×0.250\mathrm{L}}$$\text{Formality}=0.4\mathrm{F}$Therefore, the formality of $\mathrm{NaCl}$ solution is $0.4\mathrm{F}$.

Suggest Corrections
54
Join BYJU'S Learning Program
Related Videos
Redox Reactions
CHEMISTRY
Watch in App
Explore more
Join BYJU'S Learning Program