Sigh, I am starting to think that every answer on this answer key is wrong... If someone can confirm that I did this question correctly, I will just disregard the answer key for the rest of the questions.
Calculate the Ag+ concentration required to start a precipitation of AgBrO3 from a solution containing 0.50g of NaBrO3 per 0.300 litre. Ksp of AgBrO3 = 5.3(10-5)
[BrO3-] = [NaBrO3] = 0.50g(1mol/127.9g)(1/0.300L) = 0.013M
Ksp = [Ag+][BrO3-]
5.3(10-5) = [Ag+](0.013M)
4.1(10-3)M = [Ag+]
Answer key says it's 4.5(10-11)M...