What volume of a 0.303 m hydroiodic acid solution is required to neutralize 20.5 ml of a 0.167 m calcium hydroxide solution?

First, we write the reaction equation:
2HCl + Ca(OH)₂ → CaCl₂ + H₂O

From this equation, we can see that two moles of HCl are required per mole of calcium hydroxide. Moreover, we know that moles, concentration and volume are related as:

Moles = molarity * liters
n = MV

2 * Moles of Ca(OH)₂ = Moles of HCl
2 * M₁ * V₁ = M₂ * V₂
2 * 0.167 * 0.0205 = 0.303 * V₂
V₂ = 0.02259 L

The volume required is 22.60 mL