A solution is 0.20 M barium hydroxide. How many moles of nitric acid must be added to neutralize 100.0 mL of the solution?

Ba(OH)₂ + 2HNO₃ → Ba(NO₃)₂ + 2H₂O
Mole ratio Ba(OH)₂ : HNO₃ = 1 : 2

No. of moles of Ba(OH)₂ reacted = (0.20 mole/L) × (100.0/1000 L) = 0.020 mole
No. of moles of HNO₃ needed = (0.020 mole) × (2/1) = 0.040 mole

The answer: 0.040 mole

0.040

2 * 0.1 * 0.2 = 0.04 mole