A 30 ml sample of unknown strong base is neutralized after the addition of 12 ml of a 0.150 M HNO3 solution if the unknown base concentration is 0.0300 M give some possible identities for the unknown base

Answer 1

HNO3 + xBOH ==> xH2O + B(NO3)x
millimols HNO3 = 12 mL x 0.150M = 1.8
millimols base = 30 x 0.03 = 0.9. The titration step shows us that we take twice as much HNO3 as the base; therefore, the base must contain two OH groups; therefore, I would look at Mg(OH)2, Ba(OH)2, Sr(OH)2, as the unknown base. Proof:
2HNO3 + Mg(OH)2 ==> 2H2O + Mg(NO3)2
millimols HNO3 = 12 x 0.150 = 1.8
millimols Mg(OH)2 = 30 x 0.03 = 0.9
Convert mols Mg(OH)2 to mols HNO3 as
0.9 mmols Mg(OH)2 x (2 mol HNO3/1 mol Mg(OH)2) = 0.9 x 2/1 = 1.8 which is what we took of HNO3.