Chapter 5, Problem 99RQ

Both calcium chloride and sodium chloride are used to melt ice and snow on roads in the winter. A certain company was marketing a mixture of these two compounds for this purpose. A chemist, wanting to analyze the mixture, dissolved 2.463 g of it in water and precipitated calcium oxalate by adding sodium oxalate, ${\text{Na}}_{\text{2}}{\text{C}}_{\text{3}}{\text{O}}_{\text{4}}$. The calcium oxalate was carefully filtered from the solution, dissolved in sulfuric acid, and titrated with $\text{0}\text{.1000}M{\text{ KMnO}}_{\text{4}}$ solution, the reaction that occurred was

${\text{6H}}^{\text{+}}{\text{+5H}}_{\text{2}}{\text{C}}_{\text{2}}{\text{O}}_{\text{4}}{\text{+2MnO}}_4^{-}\to 10{\text{CO}}_{\text{2}}{\text{+2Mn}}^{\text{2+}}{\text{+8H}}_{\text{2}}\text{O}$

The titration required 21.62 mL of the ${\text{KMnO}}_{\text{4}}$ solution.

(a) How many moles of ${\text{C}}_{\text{2}}{\text{O}}_4^{2-}$ were present in the calcium oxalate precipitate'

(b) How many grams of calcium chloride were in the original 2.463 g sample?

(c) What was the percentage by mass of calcium chloride in the sample?