what is the minimum pH of a solution 0.1M in Mg^2    from which Mg(OH)2 will not precipiate Ksp = 1.2 * 10%-11M^-3        

Asked by gganga | 10th Apr, 2018, 06:31: PM

Expert Answer:

Mg(OH)2 dissociates as,
M g left parenthesis O H right parenthesis subscript 2 space rightwards arrow over leftwards arrow with blank on top space M g to the power of 2 plus end exponent space plus space space 2 space O H to the power of minus

T h e space s o l u b i l i t y space p r o d u c t space c o n s tan t space K s p space equals space left square bracket M g to the power of 2 plus end exponent right square bracket space space left square bracket O H to the power of minus right square bracket squared

space left square bracket O H to the power of minus right square bracket space equals space square root of fraction numerator K s p over denominator left square bracket M g to the power of 2 plus end exponent right square bracket end fraction end root space space
space left square bracket O H to the power of minus right square bracket space equals square root of fraction numerator 1.0 space cross times 10 to the power of negative 11 end exponent over denominator 0.1 end fraction end root space equals space square root of 1.0 space cross times 10 to the power of negative 10 end exponent end root space space space equals space 10 to the power of negative 5 end exponent space M

A l s o comma
space space space space space space space space space space p O H space equals space minus log left square bracket O H to the power of minus right square bracket
space space space space space space space space space space space space space space space space space equals space space minus log left square bracket 10 to the power of negative 5 end exponent right square bracket
space space space space space space space space space space p O H space equals space 5

T h e n comma
space space space space space space space space space space p O H space plus space p H space equals space 14
space space space space space therefore space space p H space equals space 14 space minus p O H
space space space space space space space space space space p H space equals space 14 space minus space 5
space space space space space space space space space space p H space equals space 9


space

Answered by Ramandeep | 11th Apr, 2018, 09:25: AM