Question

Magnesium ions can be precipitated from seawater by the addition of sodium hydroxide. How much sodium hydroxide in grams must be added to a sample of seawater to completely precipitate the 88.4 mg of magnesium present?

Answer 1

Explanation:

Solution 86P

Here, we have to determine the amount of sodium hydroxide required to precipitate all of the Mg.

Mg2+(aq) +2 NaOH(aq) ------> Mg(OH)2 (s) + 2Na+(aq)

Therefore

Molar mass of NaOH =39.997 g/mol

Molar mass of Mg =24.305 g/mol

Thus,the conversion factors

g NaOH(aq)= mol NaOH(aq) = g Mg = mol Mg

Thus the amount of sodium hydroxide required

=  88.4 mg of  Mg x x x x...