Answer
(a) $1.00\times10^{-5}\,mol$
(b) $4.00\times10^{-6}\,mol$
Work Step by Step
We find:
(a) $\text{Molarity}=\frac{\text{Moles of solute}}{\text{Liters of solution}}\implies $
$\text{Moles of solute}=\text{Molarity}\times \text{Litres of solution}$
$=0.200\,M\times50.0\times10^{-6}\,L=1.00\times10^{-5}\,mol$
(b) $\text{Moles of solute}=2.00\times10^{-3}\,M\times2.00\times10^{-3}\,L=4.00\times10^{-6}\,mol$
