Magnesium hydroxide Mg(OH)2 can be obtained by the following reaction: Mg2+ + 2 HCO3- + 2 Ca(OH)2 → 2 CaCO3- + Mg(OH)2 +

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Magnesium hydroxide Mg(OH)2 can be obtained by the following
reaction:
Mg2+ + 2 HCO3- + 2 Ca(OH)2 → 2 CaCO3- + Mg(OH)2 + 2 H2O
A 300 mL sample of mineral water was determined for magnesium
content by precipitation of the cation as Mg(OH)2. The precipitate
was filtered, washed and calcined in a crucible, obtaining MgO as
product.
Mg(OH)2 -> MgO
The mass of the crucible without sample was 25.9004 g and after
calcination the mass of the crucible plus MgO was 26.0320 g.
A) Calculate the %m/v of Mg+2 in the sample.
B) Calculate the concentration of magnesium (Mg) in the mineral
water sample, expressed in units of grams per L of H2O.