Answer
(a) 0.003195 mol
(b) $1\times10^{-6}\,mol$
Work Step by Step
We find:
(a) $\text{Molarity}=\frac{\text{Moles of solute}}{\text{Liters of solution}}\implies $
$\text{Moles of solute}=\text{Molarity}\times \text{Litres of solution}$
$=0.1255\,M\times25.46\times10^{-3}\,L=0.003195\,mol$
(b) $\text{Moles of solute}=0.020\,M\times50\times10^{-6}\,L=1\times10^{-6}\,mol$
