Question

The concentration of various cations in seawater in moles per liter are Na+ (0.46M); Mg2+ (0.056M); Ca2+ (0.01M); Al3+ (4x10^-7M); Fe3+ (2x10^-7M)
If enough OH- ion is added to precipitate 50% of the Mg2+, what mass of precipitate will be obtained from one liter or seawater

Answer 1

1L contains 0.056 M = 0.056 moles/L. Grams Mg(OH)2 = 0.056 moles x molar mass = ?? grams. Then take half of that.

Answer 2

thanks so much! just one other quick thing, how would i tell what percentage of the other ions will be precipitated?

~ i know the other answer is virtually all, but how do I come to that conclusion?