Precipitation Titration

1. Which of the following is true about Volhard's method?

• • A) It is used for the determination of chloride ions.

• • B) It involves the use of potassium chromate as an indicator.

• • C) It is a back titration method.

• • D) It is used for the determination of sulfate ions.

In Volhard’s method, which reagent is used as a back titrant?

• a) Sodium chloride

• b) Potassium chromate

• c) Ferric ammonium sulfate

• d) Ammonium thiocyanate

Which of the following is NOT a requirement for Mohr’s method?

• a) Neutral or slightly alkaline pH

• b) Presence of silver nitrate

• c) High concentration of chloride ions

• d) Presence of ferric ion as an indicator

Why is nitric acid used in Volhard’s method?

• a) To enhance the color change

• b) To oxidize silver ions

• c) To prevent the formation of silver hydroxide

• d) To dissolve the precipitate

Why is ammonium thiocyanate used in Volhard’s method instead of potassium thiocyanate?

• a) It forms a more stable complex

• b) It prevents unwanted side reactions

• c) It provides better solubility

• d) It is less reactive with ferric ions

In Fajan’s method, which factor influences the adsorption of the indicator on the precipitate surface?

• a) Ionic strength of the solution

• b) The color of the indicator

• c) The solubility of the precipitate

• d) The type of titrant used

In Volhard’s method, why is silver nitrate added in excess to the sample?

• a) To ensure complete reaction with chloride ions

• b) To form a soluble complex with thiocyanate

• c) To shift the equilibrium in favor of precipitation

• d) To prevent interference from sulfate ions

What is the primary limitation of Mohr’s method?

• a) It cannot be used for bromide ion determination

• b) It requires acidic conditions

• c) It is affected by pH changes

• d) It cannot be used with adsorption indicators

Why is nitric acid preferred over hydrochloric acid in Volhard’s method?

• a) HCl reacts with silver ions

• b) HNO₃ acts as an oxidizing agent

• c) HNO₃ prevents the formation of silver chloride precipitate

• d) HNO₃ enhances the reaction rate

The primary reaction in Volhard’s method is:

• a) Ag⁺ + Cl⁻ → AgCl

• b) Ag⁺ + SCN⁻ → AgSCN

• c) AgCl + SCN⁻ → AgSCN + Cl⁻

• d) Fe³⁺ + SCN⁻ → Fe(SCN)³