What volume of a 0.132 M potassium hydroxide solution is required to neutralize

Question

What volume of a 0.132 M potassium hydroxide solution is required to neutralize 15.6 mL of a 0.327 M hydrobromic acid solution? A 13.2 g sample of an aqueous solution of perchloric acid contains an unknown amount of the acid. If 20.8 mL of 0.324 M potassium hydroxide are required to neutralize the perchloric acid, what is the percent by mass of perchloric acid in the solution? A 0.5234 ft sample of a pure soluble chloride compound is dissolved in water, and all of the chloride ion Is precipitated as AgCl by the addition of an excess of silver nitrate. The mass of the resulting AgCl is found to be 1.4210 g. What is the mass percentage of chlorine in the original compound?

Explanation / Answer

28)

KOH + HBr KBr + H2O

There is 1:1 molar relationship between the moles of HBr and moles of KOH

So, moles HBr = moles KOH

Since moles = molarity x volume

Therefore,

(Molarity HBr x volume HBr) = (molarity KOH x volume KOH)

0.327M x 15.6 ml = 0.132 M x volume KOH

Volume of KOH = 0.327M x 15.6 ml / 0.132 M

                              =38.65 ml

29)

HClO4 + KOH KClO4 + H2O

Step-1 Calculate the moles of KOH-

Moles of KOH= 0.324 moles/L x 1L/1000ml x 20.8 mL = 0.006739 moles

Step- 2 Calculate the mass of Perchloric acid

There is 1:1 molar relationship between the moles of HClO4 and moles of KOH

So, moles HClO4 = moles KOH

Moles HClO4 = 0.006739 moles

Molar mass of Perchloric acid is 100.4585 g/mol

Mass of Perchloric acid = Moles HClO4 x Molar mass of Perchloric acid

                                           = 0.006739 moles x 100.4585 g/mol

                                           = 0.677 g

Step -3

The percent by mass of perchloric acid in the solution = 0.677 g/13.2 g x 100

Mass of perchloric acid in the solution = 5.12 %

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