A saturated 0.01 M `H_(2)` S solution is buffered at pH =3 with exactly sufficient Pb`(NO_(3))_(2)` to not precipitate Pbc. `K_(a) ` of `H_(2) S = 10^(-23),K_(sp)` of Pbs = `10^(-28)` . The concentration of `Pb^(+2)` in the solution is `10^(-x)` . What is x ?

Answer

9

Explanation

` H_2S hArr 2H^(+) +S^(_2) rArr K_a =([H^(+)]^(2) [S^(-2)])/( [H_2S]) `
` pH =3 rArr [H^(+) ] =10 ^(_3) M`
` 10 ^(-23) =( 10 ^(-6) [S^(-2)])/( 10^(-2) ) rArr [S^(-2) ] =10 ^(-19) M`
` PbShArr Pb^(+2) +S^(-2)`
` K_(sp) =[pb^(+2) ][S^(-2) ] rArr 10 ^(-28) =[pb^(+2) ] 10 ^(-19) `
` [pb^(+2) ] =10 ^(-9) M`