How many moles of `Ca(OH)_(2)` must be dissolved to produce 250 mL of an aqueous solution of pH `10.65`, assuming completer dissociation ?

Answer

`5.6 xx 10^(-5) " moles"`

Explanation

pH of the solution =10. 65 , pOH of the solution =(14 -10.65) =3.35
`log [(1)/(OH^(-))] = 3.35 " or " [(1)/(OH^(-))] = " Antilog " 3.35 =2238. 72`
`[OH^(-)] =(1)/(2238.72) =4.47 xx 10^(-4) " moles"//L =(4.47 xx 10^(-4))/(4)`
`= 1.12 xx 10^(-4) " moles"// 250 mL`
No . of moles of `Ca(OH)_(2)` dissolved `= (1)/(2) xx 1.12 xx 10^(-4) =0.56 xx 10^(-4) =5.6 xx 10^(-5)" moles "`