Question

The solubility of Sr `(OH)_(2)` at 298K is 19.23 g/L of solution. Calculate the concentrations of strontium and hydroxyl ions and the pH of the solution. (Atomic mass of Sr = 87.6)

Answer 1

Molar mass of Sr `(OH)_(2) = 87.6+34=121.6 g "mol" ^(-1)`
Solubility of Sr `(OH)_(2) ` in moles `L^(-1)=(19.23g L^(-1))/(121.6g "mol"^(-1))=0.1581M`
Assuming complete dissociation , Sr`(OH)_(2)rarrSr^(2)+2OH^(-)`
`:. [Sr^(2+)]=0.1581 M, [OH^(-)]=2xx0.1581=0.3162`M
`pOH=-log 0.3162=0.5, :. pH = 14-0.5=13.5`