Two solutions of a substance (non-electrolyte) are mixed as follows: 480 mL of a 1.5 M solution and 520 mL of a 1.2 M solution. What is the molarity of the final mixture?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 1.344 M
On mixing, the moles of solute add up and the volumes add up. Moles in each solution = molarity × volume (in L):
\( \displaystyle M=\frac{M_1V_1+M_2V_2}{V_1+V_2} \)
\( \displaystyle M=\frac{(1.5\,\mathrm{M}\times0.480\,\mathrm{L})+(1.2\,\mathrm{M}\times0.520\,\mathrm{L})}{0.480\,\mathrm{L}+0.520\,\mathrm{L}}=\frac{0.720\,\mathrm{mol}+0.624\,\mathrm{mol}}{1.000\,\mathrm{L}} \)
\( \displaystyle M=1.344\,\mathrm{M} \)
The molarity of the final mixture is 1.344 M.