8/18/2019 Back Titration of Ammonia

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Title: Back Titration of Ammonia

Aim: To determine the percentage of ammonia in an ammonium salt providedusing a back titration.

Apparatus: Three 250 cm3 conical asks, 25 cm3 pipette, to 200 cm3 beakers,

one !00cm3 beaker, one 250 cm3 beaker, "lter funnel, safet# goggles, 50 cm3 burette, red litmus paper, burner, tongs, pipette "ller

Materials: screened meth#l red indicator, 0.!$ ammonium chloride solution, 0.!$sodium h#dro%ide solution, 0.! $ h#drochloric acid solution, distilled ater

Procedure& All glassare ere thoroughl# ashed cleaned. A 25 cm3 pipette asthen rinsed tice ith a small amount of ammonium chloride solution. 25 cm3 of

ammonium chloride as then pipetted into three 250cm3 conical asks each. 50

cm3 of 'a() as then pipetted into each conical ask, and then placed on burner

to boil. (nce the solution in the ask began to boil, and it as noted that the

solution volume decreased* distilled ater as added. The vapour escaping the

ask as checked intermittentl# ith a strip of red litmus paper until the vapour no

longer turned a strip of red litmus blue. The ask as then removed from the heat

and as placed under a running stream of ater to cool.

(nce cooled, 3 drops of meth#l red ere added to the ask, observations ere

noted.

A hite tile as placed on the base of the burette stand beneath the burette. The

"rst ask as placed on the hite tile and the solution in it graduall# titrated ith

)+l from the burette. The burette tap as turned o from time to time to allo

solution on the side of the burette to drain don to the solution. 'ear the end point

the titration as carried out more slol#, then drop b# drop until a single drop from

the burette caused a permanent colour change. The volume of )+l used as

recorded in the table as "nal volume for the trial titration.

 The volume of )+l in the burette as replenished and the other to back titrations

carried out, this time more rapidl#, until a volume of about 2.00 cm3 less than the

volume used in the rough titration as run into the titration ask, the tap turned o

and then on to slol# add the )+l to the ask then drop b# drop until the end point

as reached. The initial and "nal volumes of )+l used for each titration as

recorded in the table.