1) Which of the following concentrations of NH4 + will be sufficient to
prevent the precipitation of Mg(OH)2 from a solution which is 0.01 M in
MgCl2 and 0.1 M NH3 (aq). Given that Ksp of Mg (OH)2 =
2.5 x 10-11 and Kb for NH3 (aq) = 2 x 10-5 .
[A] 0.01M [B] 0.02M [C] 0.001M [D] 0.04M
2) A buffer solution is made by mixing a weak acid HA (Ka = 10-6 ) with its salt NaA in equal amounts. What should be the amount of acid or salt that should be added to make 90 ml of buffer solution of butter capacity 0.1 ?
[A] 10 m moles [B] 22 m moles [C] 9 m moles [D] 11 m moles
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