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# During a laboratory activity, a student places 20.0 mL of HCl(aq) of unknown concentration into a fl

Regents Chemistry Exam August 2022

During a laboratory activity, a student places 20.0 mL of HCl(aq) of unknown concentration into a flask. The solution is titrated with 0.10 M KOH(aq) until the HCl(aq) is exactly neutralized. At the end of the titration, the volume of KOH(aq) added is 42.0 mL. During the laboratory activity appropriate safety equipment was used and safety procedures were followed.

74 Compare the number of moles of H+(aq) ions to the number of moles of OH-(aq) ions in the titration mixture when the HCl(aq) is exactly neutralized by the KOH(aq). 

In a titration procedure, when acid and base are neutralized, the number of moles of H+ must be equal to the number of moles of OH-.

Answer: The number of hydrogen ions is equal to the number of hydroxide ions.

75 Determine the concentration of the HCl(aq) solution using the titration data. 

According to Table T on the Reference Table, the formula for titration is MaVa = MbVb where Ma = molarity of acid, Va is volume of acids, Mb is molarity of base and Vb is volume of base.

The acid is HCl and the base is KOH

Ma = ?

Va = 20.0 mL

Mb=0.10 M

Vb = 42.0 mL

Now, lets plug it in.

Ma(20.0 mL ) = 0.10 M(42.0 mL)