Solid $\mathrm{B}\mathrm{a}(\mathrm{N}{\mathrm{O}}_3{)}_2$ is gradually dissolved in a $1.0\times 10^{-4}$ $\mathrm{M}$ $\mathrm{N}{\mathrm{a}}_2\mathrm{C}{\mathrm{O}}_3$ solution. At what concentration of $\mathrm{B}{\mathrm{a}}^{2+}$ will a precipitate begin to form? $\left[{\mathrm{K}}_{\mathrm{s}\mathrm{p }}\mathrm{}\mathrm{f}\mathrm{o}\mathrm{r }\mathrm{}\mathrm{B}\mathrm{a}\mathrm{C}{\mathrm{O}}_3=5.1\times 10^{-9}\right]$

• Correct answer
  A

  $5.1\times 10^{-5}$ $\mathrm{M}$
• B

  $8.1\times 10^{-8}$ $\mathrm{M}$
• C

  $8.1\times 10^{-7}$ $\mathrm{M}$
• D

  $4.1\times 10^{-5}$ $\mathrm{M}$

Hence, the correct answer is option: 'A'.