The balanced equation for the given titration reaction can be written as
Step 1 : Find moles of Ca(OH)₂
Volume of Ca(OH)₂ = 20 mL
Concentration of Ca(OH)₂ = 5.00 x 10⁻³ M
Moles of Ca(OH)₂ =
Moles of Ca(OH)₂ = 1.00 x 10⁻⁴
Step 2 : Find moles of HNO3 using mole ratio from balanced equation
The mole ratio of HNO₃ and Ca(OH)₂ is 2 : 1
Let us use this as a conversion factor to find moles of HNO₃.
Moles of HNO₃ =
Moles of HNO₃ = 2.00 x 10⁻⁴
Step 3 : Find concentration of HNO3
Concentration of HNO3 can be calculated as
The concentration of HNO₃ is given as 5.00 x 10⁻³
Moles of HNO3 = 2.00 x 10⁻⁴
Let us plug in these values in above equation.
Volume of HNO₃ in mL =
Volume of HNO₃ needed for titration is 40 mL