In a 0.250*mol*L^-1 solution, what molar quantity is associated with a 0.200*L volume?

${n}_{\text{solute}}$ $=$ $0.05 \cdot m o l$
$\text{Concentration}$ $=$ $\text{Moles of solute"/"Volume of solution (L)}$.
Thus, $\text{Moles of solute}$ $=$ $\text{Concentration "xx" Volume}$.
$=$ $0.250 \cdot m o l \cdot \cancel{{L}^{-} 1} \times 0.200 \cdot \cancel{L}$ $=$ $0.0500 \cdot m o l$.