Question

AgNO3 used as precipitating agent in mohr's method against​

Answer 1

Explanation:

Silver chloride is very insoluble in water. Addition of AgNO3 to a solution containing chloride ions results in formation of a finely divided white precipitate AgCl. This reaction provides a basis for determination of chloride ions.

Answer 2

Answer:

Silver nitrate is used as a precipitating agent against sodium chloride (or halogen compounds except iodine compounds) in mohr's method.

Explanation:

• Mohr's method is also called the argentometric method.

• It is a titration method in which silver compound is used as standard to analyse chloride ion concentration.

• Silver nitrate reacts with sodium chloride in the presence of the potassium chromate (5%) as an indicator. As a result of the reaction silver chloride precipitates out in the form of white precipitate (primary precipitate) and sodium nitrate will be the by-product.

                           $AgNO_{3} + NaCl \longrightarrow AgCl + NaNO_{3}$

• The pH maintained in the mohr's method is neutral (pH = 7).

• Silver chloride precipitates early because of its lower ionic value.

• Once the silver nitrate gets completely reacted with sodium chloride then it reacts with the indicator (potassium chromate).

• Silver nitrate reacts with potassium chromate and forms silver chromate which converts white precipitate into reddish brown precipitate (secondary precipitate) which is the end point of the mohr's method.

                        $2AgNO_{3}+ K_{2}CrO_{4}\longrightarrow Ag_{2}CrO_{4}+2KNO_{3}$

• All the halogen compounds can be analyzed by mohr's method except Iodine compounds because iodine forms primary reddish brown precipitate therefore the end point cannot be determined.