Question

Sodium hydroxide is added to a solution that contains 0.049 MA13+ and 0.011 M Mg2+. The concentration of the first ion to precipitate (either A13+ or Mg2+) decreases as its precipitate forms. Which cation precipitates out first and what is the concentration left of this ion when the second ion begins to precipitate ? Select the correct answer. cross out Select one: O A. Mg2+ precipitates out first and there is still a high percentage of Mg2+ left in solution when A13+ precipitates Cross out O B. Mg2+precipitates out first and there is 2.8 x 10-6 M left in solution when A13+ precipitates O C. A13+ precipitates out first and there is practically no A13+ left in solution when Mg2+precipitates cross out O D. Mg2+ precipitates out first and there is practically no Mg2+ left in solution when A13+ precipitates cross out O E. A13+precipitates out first and there is still a high percentage of A13+ left in solution when Mg2+precipitates o F. A13+ precipitates out first and there is 8.73 x 108 MA13+ left in solution when Mg2+ precipitates cross out cross out

Answer 1

Mg(OH) = 11x10 a Solubility product of Al(OH)3 = 2.0x1032 at 25°c solubility Product of the salubility product of Alcott is much less than that it ng (OH). So when NaOH) added to the solution then Astion will precipitate first in the form of fat Al(OH), But do due to its sparingly solubility in water a trace amount of Al 3t will present in water, Al(OH)₂ (aq) A1²+ & sot Let the solubility of Al (Olt) = x (M) . . e concentration of Al3+ =[A13] = x (M) Concentration of (OH) = [OH-] = 3x (M). . [Apst] [OH-] 3 = Kesp. xx (3x)² = ksp 27 xt = tsp 27 n = 2.0818-32 a = 5:22710-9m. CAP3} = 5.22 7 109 M. I & So practically no Alst present in the solution. & Answer is (e Al3+ precipitates out first and there is no practically Al3+ left in the solntion when rgat Precipitates. с