Question

What will be the molality of the solution made by dissolving $10g$ of $NaOH$ in $100g$ of water?

• A. $2.5m$
• B. $5m$
• C. $10m$
• D. $1.25m$

Answer 1

The correct option is A $2.5m$

Molality $=\frac{numberofmolesofsolute}{massofsolvent\left(kg\right)}$

and number of moles $=\frac{mass}{molarmass}$

For NaOH, mass = 10g, molar mass = 40 g/mol

and water, mass = 100g = 0.1 kg

Thus, molality$=\frac{10}{40\times 0.1}=2.5m$