Sunday, July 9, 2017

2.48: Describe Tests for these Anions: Cl-, Br- and I- Using Acidified Silver Nitrate Solution, SO42- Using Acidified Barium Chloride Solution, CO32- Using Hydrochloric Acid and Identifying the Gas Evolved



ANIONS: Negatively charged ion
s
TEST FOR Cl-, Br- and I- :
s
TEST FOR CHLORIDE, BROMIDE AND IODIDE
Diagram showing the Test for Cl-, Br- and I-
METHOD:

  • Add a small volume of Dilute Nitric Acid to react and remove Carbonate ions from sample solution
  • Add a few drops of Silver Nitrate Solution
  • Colour of precipitate is observed and recorded

RESULT AND EQUATION:
HALIDE ION PRESENT
COLOUR OF PRECIPITATE
EQUATION
CHLORIDE ION  Cl-
White Precipitate
Ag+    +    Cl-    →    AgCl
BROMIDE ION    Br-
Cream Precipitate
Ag+    +    Br-    →    AgNr
IODIDE ION         I-
Yellow Precipitate
Ag+    +    I-    →    Agl
s
s

TEST FOR SO4 :
s
TEST FOR SULFATE IONS
Diagram showing the Test for Sulfate Ions
METHOD:

  • Add a small volume of Dilute Hydrochloric acid to react and remove Carbonate ions
  • Add a few drops of Barium Chloride Solution
  • Colour of precipitate is observed and recorded

RESULT:

  • If Sulfate ions are present, White precipitate will form (Barium Sulfate)

EQUATION:



  Ba2+ (aq)      +         SO4-  (aq)      →         BaSO4 (s)             

s
s
TEST FOR CO3 :
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TEST FOR CARBONATE IONS
Diagram showing the Test for Carbonate Ions
METHOD:

  • Add Dilute Hydrochloric acid
  • Gas produced is bubbled into limewater
  • Colour of precipitate is observed and recorded

RESULT:

  • If Carbonate ions are present, limewater will turn milky

EQUATION:



  CO32- (aq)      +         2H+  (aq)      →         CO2 (g)         +         H2O  (l)             

5 comments:

  1. Error in carbonate ion test. Need to remove "Colour of Precipitate is Observed and Recorded"

    ReplyDelete
  2. So, whats the difference between Carbon dioxide test and Carbonate ions test they both have the same results

    ReplyDelete
    Replies
    1. you add HCl first, so if a carbonate is present, the carbonate becomes C02, which you can then test for

      Delete
  3. In the Carbonates test could you please tell me why H is present instead of HCl in the equation.

    ReplyDelete
    Replies
    1. the Cl- is just floating around in the solution, together with whatever the carbonate was bonded to before

      Delete