To estimate the amount of barium as BaCrO4 in the solution of barium chloride

o estimate the amount of barium as BaCrO4 in the solution of barium chloride

1. SHREE MALLIKARJUN COLLEGE TYBSC
SAFETY: Refer to MSDS of barium chloride, barium nitrate, potassium dichromate, ferric chloride, ammonium chloride,
ammonium hydroxide, hydrochloric acid.
-Dr. Mithil S. Fal Desai

Aim: To estimate the amount of barium as BaCrO4 in the solution of barium chloride-containing ferric
chloride and free HCl.
Chemicals: Ba salt (barium chloride, barium nitrate), potassium dichromate, ferric chloride, ammonium
chloride, ammonium hydroxide, hydrochloric acid.
Apparatus: Beaker, conical flask, funnel, Whatman 41, G4 crucible, glass rod with policemen, water bath,
oven.
Theory: Barium (Ba
2+
) and ferric (Fe
3+
) ions are separated by precipitation of Fe as ferric hydroxide. As
barium hydroxide is soluble, the ferric hydroxide is filtered off. The filtrate containing barium is acidified
and reacted with potassium dichromate. The resultant yellow precipitate is washed with distilled water and
dried in the oven at 110 °C and weighed as BaCr2O7 in a G4 crucible.
Reaction:
Ba
2+
(aq) + Fe
3+
(aq) + 3(OH)
-
(aq)  Fe(OH)3↓+ Ba(OH)2 (soluble)
2Ba
2+
(aq) + (Cr2O7)
2-
(aq) + H2O(aq)  2BaCrO4↓ + 2H
+
(aq)
Procedure:
1) Pipette out 25 mL of a solution having a mixture of Ba
2+
and Fe
3+
ions in a 250 mL beaker.
2) Add 10 mL of 6 M ammonium hydroxide and digest the precipitate on the water bath.
3) After 30 min, cool the solution and add 1-2 mL of ammonium hydroxide along the sides of the beaker
and check for complete precipitation.
4) Transfer the precipitate to filter paper and wash the precipitate with 20 mL of distilled water.
5) Acidify the filtrate with dilute HCl and add 10 mL of potassium dichromate.
6) Digest the precipitate on the water bath for 20 min and cool the solution.
7) Transfer the precipitate in G4 crucible with known weight and wash the precipitate using distilled water
until filtrate shows a negative test for chloride and dichromate ions.
8) Dry the G4 crucible in an oven for 45 min at 110 C.
9) Cool and weigh the crucible containing the precipitate.
(To get constant weights to repeat the step 8 and 9)
8) The weight of precipitate quantitatively corresponds to the weight of BaCrO4.
Observation
Table 1.
The constant
weight of G4
crucible without
precipitate
“W1’ (g)
The constant
weight of G4
crucible with
precipitate
“W2’ (g)
Weight of
BaCrO4
‘A’=W2 – W1 (g)
Molecular weight
of BaCrO4
‘B’ (g)
Atomic weight of
Ba
‘C’(g)

Amount of Ba in
25 mL
‘x' = A* C/B (g)

Result: Amount of Ba in 500 mL is ______g.