Chemistry - Concentration Terms Question with Solution | TestHub

The number of moles of solute remains constant during dilution. Initial moles of $\text{HCl}=M_1{V}_1=0.5\text{M}\times 0.200\text{L}=0.1\text{mol}$. The final volume of the solution is the sum of the initial volume and the added water volume: $V_2=200\text{mL}+300\text{mL}=500\text{mL}=0.500\text{L}$. The final molarity $M_2=\frac{\text{moles of solute}}{\text{final volume}}=\frac{0.1\text{mol}}{0.5\text{L}}=0.2\text{M}$. Therefore, option A is correct.