Calculate the molarity of a solution containing 5 g of NaOH in 450 mL of solution.
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 0.278 M
Molarity is the number of moles of solute in 1 litre of solution. Molar mass of \( \ce{NaOH} \) = 23 + 16 + 1 = 40 g mol−1.
\( \displaystyle M=\frac{n_{\text{solute}}}{V_{\text{solution}}\ (\mathrm{L})} \)
\( \displaystyle n=\frac{5\,\mathrm{g}}{40\,\mathrm{g\,mol^{-1}}}=0.125\,\mathrm{mol} \)
\( \displaystyle M=\frac{0.125\,\mathrm{mol}}{0.450\,\mathrm{L}}=0.278\,\mathrm{mol\,L^{-1}}=0.278\,\mathrm{M} \)