lab 3

Qualitative Anion Tests

Michele Hopkins

General Chemistry II/ CHEM-182-DL1

Professor Amal Bassa

July 27, 2014

Introduction

Qualitative Anion Tests

Peter Jeschofnig, Ph.D. Version 42-0192-00-01

Lab Report Assistant

This document is not meant to be a substitute for a formal laboratory report. The Lab Report Assistant is simply a summary of the experiment’s questions, diagrams if needed, and data tables that should be addressed in a formal lab report. The intent is to facilitate students’ writing of lab reports by providing this information in an editable file which can be sent to an instructor.

Observations

3

Questions

Classify your ions according to the following three groups. Several of the cations belong to more than one group.

Group 1: Anions that WILL NOT PRECIPITATE in the presence of silver nitrate.

According to our experiment, the only Anion that will not precipitate is Sulfate.

Group 2: Anions that WILL PRECIPITATE in the presence of silver nitrate and the resulting precipitates WILL DISSOLVE upon acidification with nitric acid.

In my observation in the experiment, the only two Anions are Carbonate and Phosphate.

Group 3: Anions that WILL PRECIPITATE in the presence of silver nitrate and the resulting precipitates WILL NOT DISSOLVE upon acidification with nitric acid.

The only Anions that were affected this way are Bromide, Chloride, Iodide, and Sulfide.

A. Write a net ionic equation for any reaction that produces a precipitate.

Sodium Iodide: Ag+ (aq) + I- (aq) → AgI (s)

Sodium Bromide: Ag+ (aq) + Br- (aq) → AgBr (s)  Sodium Sulfide: Ag+2 (aq) + S2- (aq) → Ag2S (s) 

Sodium Chloride: Ag+ (aq) + Cl- (aq) → AgCl (s)  Sodium Phosphate: Ag+ (aq) + PO4- (aq) → Ag3PO4 (s) 

Sodium Carbonate: Ag+2 (aq) + CO32- (aq) → Ag2CO3 (s) 

B. Identify the anions that produce gas upon addition of HCl.

The anions that produced gas upon the addition to the experiment are Carbonate and Sulfide.

C. Identify the anions that do not precipitate with silver nitrate.

The anions that do not precipitate with silver nitrate are Sulfate.

D. Identify the anions that react with silver nitrate to form precipitates that dissolve when acidified with nitric acid.

The two anions that reacted with silver nitrate to form precipitates that dissolves when acidified with nitric acid during the experiment was Carbonate and Phosphate.

E. Identify the anions that react with silver nitrate to form precipitates that do not dissolve when acidified with nitric acid.

The four anions that reacted with silver nitrate to form precipitates that do not dissolve when acidified with nitric acid during the experiment are Bromide, Chloride, Iodide, and Sulfide.

F. What simple test (other than a specific confirmation test) would distinguish between CO3 2-

and NO3 - ? Add Barium Chloride to the anions, if a white precipitate of BaCO3 forms then that unknown substance contains CO3 2-.

Conclusion

Reference

© Hands-On Labs, Inc. LabPaq CK-01

Data Table: Qualitative Anion Tests�

�

Name�

Test Tube 1

w/HCl�

Test Tube 2 w/AgNO3�

w/HNO�

Test Tube 3

Confirmation�

�

Bromide�

Gas�

Milky White Precipitate�

Precipitate does not dissolve�

No Reaction�

�

Carbonate�

Gas�

Milky White Precipitate�

Precipitate dissolves�

No Reaction�

�

Chloride�

No Reaction�

Milky White Precipitate�

Precipitate does not dissolve�

No Reaction�

�

Iodine�

No Reaction�

Milky Yellow Precipitate�

Precipitate does not dissolve�

No Reaction�

�

Phosphate�

Gas�

Milky Yellow Precipitate�

Precipitate dissolves�

No Reaction with warming�

�

Sulfate�

Gas�

No Reaction�

No Reaction�

Milky White Precipitate�

�

Sulfide�

Gas�

Yellow-Brown Precipitate�

Precipitate does not dissolve�

No Reaction�

�

Unknown�

Gas�

No Reaction�

No Reaction�

Milky White Precipitate�

�