Part 1: Assume that 10.50 g of HNO3 reacts. How many moles of HNO3 does this represent? Answer: 0.1666 mol HNO3.
Part 2: How many moles of Ba(OH)2 must be present to react with 10.50 g of HNO3 in order for a complete reaction to occur with no reactants left over? 2HNO3 (aq) + Ba(OH)2 (aq) → Ba(NO3)2 (aq) + 2H2O (l). Mol Ba(OH)2.