Solid $\mathrm{Ba}{\left({\mathrm{NO}}_3\right)}_2$)i is gradually dissolved in a $1.0\times {10}^{-4}\mathrm{M}{\mathrm{Na}}_2{\mathrm{CO}}_3$. solution. At what concentration of ${\mathrm{Ba}}^{2+}$ will a precipitate begin to form? (Given:$K_{\mathrm{sp}}=5.1\times {10}^{-9}{\mathrm{M}}^2\text{ for }{\mathrm{BaCO}}_3.$ .)