Question

An aqueous solution of calcium hydroxide is standardized by titration with a 0.112 M solution of hydrobromic acid. If 15.2 mL of base are required to neutralize 12.4 mL of the acid, what is the molarity of the calcium hydroxide solution?

Answer 1

0.0457 M

Step-by-step explanation:

The reaction that takes place is:

• 2HBr + Ca(OH)₂ → CaBr₂ + 2H₂O

First we calculate how many moles of acid reacted, using the HBr solution's concentration and volume:

• Molarity = Moles / Volume

• Molarity * Volume = Moles

• 0.112 M * 12.4 mL = 1.389 mmol HBr

Now we convert HBr moles to Ca(OH)₂ moles, using the stoichiometric ratio:

• 1.389 mmol HBr *
  `(1mmolCa(OH)_(2))/(2mmolHBr)` = 0.6944 mmol Ca(OH)₂

Finally we calculate the molarity of the Ca(OH)₂ solution, using the given volume and calculated moles:

• 0.6944 mmol Ca(OH)₂ / 15.2 mL = 0.0457 M