Determine unknown volume

Question

Calculate the volume of 6.93x10^-2 M calcium hydroxide required to neutralize 28.2 mL of a 0.147 M hydrochloride acid solution.

Answer 1

Write the correctly balanced equation:

Ca(OH)₂ + 2HCl ==> 2H₂O + CaCl₂ ... balanced equation

Calculate moles of HCl present:

28.2 ml x 1 L/1000 ml x 0.147 mol/L = 0.004145 moles

Calculate moles Ca(OH)₂ needed to react with this amount of HCl:

0.004145 mol HCl x 1 mol Ca(OH)₂ / 2 mol HCl = 0.002073 moles Ca(OH)₂ needed

Finally, calculate volume of 6.93x10^-2 M Ca(OH)₂ equivalent to this many moles:

6.93x10^-2 M = 0.0693 mol/L

0.0693 mol/L (x L) = 0.002073 moles

x = 0.02991 L = 29.9 mls of Ca(OH)₂ required (3 sig. figs.)