Barium dithionate, $\text{BaS}_2\text{O}_6\cdot2\text{H}_2\text{O}$, dissolves in water. $\text{S}_2\text{O}_6^{2-}$ ions decompose slowly in acidic solution. $\text{S}_2\text{O}_6^{2-}(\text{aq}) \rightarrow \text{SO}_2(\text{g}) + \text{SO}_4^{2-}(\text{aq})$ A mass of $3.513\,\text{g}$ of $\text{BaS}_2\text{O}_6\cdot2\text{H}_2\text{O}$ is dissolved in water in a $100\,\text{cm}^3$ volumetric flask, and the flask is then filled to the mark with $\text{HCl(aq)}$. At time $x$ min, a white precipitate with mass $0.661\,\text{g}$ is present in the flask. Calculate the concentration of $\text{BaS}_2\text{O}_6$ in the volumetric flask at time $x$ min?
- A$0.0077\,\text{mol dm}^{-3}$
- B$0.0090\,\text{mol dm}^{-3}$
- C$0.077\,\text{mol dm}^{-3}$
- D$0.090\,\text{mol dm}^{-3}$