$5.72~g$ of $Na_{2}CO_{3} \cdot 10H_{2}O$ ($M_{r}=286~g\cdot mol^{-1}$) is dissolved in water to prepare $0.4~dm^{3}$ of aqueous solution. What is the concentration of sodium ions, in $mol\cdot dm^{-3}$, in the resulting solution?
$5.72~g$ of $Na_{2}CO_{3} \cdot 10H_{2}O$ ($M_{r}=286~g\cdot mol^{-1}$) is dissolved in water to prepare $0.4~dm^{3}$ of aqueous solution. What is the concentration of sodium ions, in $mol\cdot dm^{-3}$, in the resulting solution?