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Sulfite, Carbonate, and Ammonium Tests

Process Objectives

•         Predict which qualitative test to use in identifying an unknown ionic compound.

·          Experiment with qualitative tests to determine the identity of unkown ionic compounds

Learning Objective

•         Become familiar with the chemistry of common ionic compounds.

Apparatus

Burner and tubing                                

5-cm length of No. 24 platinum wire, sealed at the opening of a glass tubes 10 cm long. If plati­num wire is not available, nichrome wire (not as satisfactory as platinum) may be used. Nichrome wire should be held with forceps

1 spot plate or 3 small test tubes               

Sparker.

Materials

hydrochloric acid, 3 M sodium hydroxide, 3 Mred litmus paper

filter paper, cut into short strips sodium carbonate, solid

sodium sulfite, solid

ammonium chloride, solid

potassium permanganate, 0.1 M

potassium ferricyanide, 0.1 M

potassium ferrocyanide, 0.1 M

 Recording Your Observations

Use your Data Table to record your observations.

 CAUTION: Whenever you handle acids or bases, wear safety goggles, apron, and gloves. Avoid contact with skin and eyes. Avoid breathing vapors. If any acid or base should spill on you, im­mediately flush the area with water and then notify your teacher.

 Procedures

1.      To a few crystals of sodium sulfite in a spot plate or small test tube, add two drops of 3 M HC1. With forceps quickly hold a strip of filter paper moist­ened with 0.1 M KMnO₄over the solution. See Figure 9-1. This reaction is characteristic of the sulfite, SO₃^2-, ion.

 Observation:___________________________________________________ _____________________________________________________________ _____________________________

2.      To a few crystals of sodium carbonate in a spot plate orsmall test tube, add two drops of 3 M HC1. With forceps quickly hold a small strip of filter paper moistened with 0.1 M KMnO₄, over the solution. This reaction is character­istic of the carbonate, CO₃ion.

 Observation:___________________________________________________ _____________________________________________________________ ______________________

 3.      Afew crystals of ammonium chloride in a spot plate or small test tube, add two drops of 3 M NaOH. Quickly hold a piece of moistened red litmus paper over the solution as shown in Figure 9-2. This reaction is characteris­tic of the ammonium ion.

 Observation:___________________________________________________ _____________________________________________________________ ________________ 

Data Table

	HCl	Litmus Paper/KMnO4	NaOH
Sulfite ion
Carbonate ion
Ammonium ion

Questions

Strategy for Predicting

Consider all four ions in order to determine which test is appropriate. Review all of the tests. A useful test will give different results with each of the compounds. You should be able to predict the results for each compound before you begin the test.

 1.Explain how to generate ammonia gas in the laboratory. Write and balance the equation for the reaction.