Question

Borax (na2b4o7·10h2o; fw = 381.372 g/mol; density = 1.73 g/ml), a primary standard, was used to standardize a solution of hno3. titration of 0.2619 g of borax required 21.61 ml. what is the molarity of the hno3

Answer 1

0.06355391 mol The balanced equation for the reaction is Na2B4O7*10H2O + 2 HNO3 = 2 NaNO3 + 4 H3BO3 + 5 H2O So for each mole of Borax to neutralize, it takes 2 moles of HNO3. Calculate number of moles of Borax 0.2619 g / 381.372 g/mol = 0.0006867 mol Moles of HNO3 used = 0.0006867 mol * 2 = 0.0013734 mol Molarity is defined as moles per liter so divide the number of moles used by the volume in liters. So 0.0013734 / 0.02161 = 0.06355391 mol