Question #fa00c

1 Answer
il maestro
May 4, 2015

Yes, a precipitate will form.

A solution with pH 8.5 has a pOH of 14-8.5 = 5.5, therefore #[OH^-]#= #3.16*10^-6#. The dilution of 12.5 ml to 25 ml brings this concentration to #[OH^-]#= #1.58*10^-6#.
#[Al^(3+)]*[OH^-]^3# = #(3.5*10^-8)/2*(1.58*10^-6)^3 #=#1.75*10^-8*4.74*10^-18#= #8.29*10^-26#
This value exceeds the ksp of #3.1*10^-34#, and a precipitation will occur.

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