Experiment - Tests on Inorganic Ions

Introduction

You are provided with a series of labeled aqueous solutions containing various cations (positive ions) and anions (negative ions) as well as sodium hydroxide(aq), ammonium hydroxide(aq), silver nitrate(aq), lead nitrate(aq), barium chloride(aq), hydrochloric acid(aq), nitric acid(aq) and Devarda's alloy. Perform the reactions as detailed below in stages 1, 2 and 3 completing the tables where appropriate.

Method - Stage 1

Take 2 test tubes and pipette one of the cation solutions into each of the test tubes, to a depth of about 1 cm.

To one of the test tubes add 5 drops of sodium hydroxide(aq) from the bottles in the lab. Note all observations in the table below.

Then fill the tube up to a depth of about 5 cm with the sodium hydroxide(aq) and again note your observations down in the table.

Then repeat the above procedure in the second test tube, but use ammonium hydroxide(aq) in place of the sodium hydroxide(aq).

Stage 2

As a revision exercise perform the tests for various anions as detailed in the table below. Complete the observations for the table.

Stage 3

The final part of the practical work involves the use of all the observations you have made so far.

There are 3 solutions labelled X, Y and Z in the laboratory. Each of them contains one cation and two anions. To find out what the components of each solution perform the following routine.

Take 6 test tubes and pipette about a cm depth of one of the unknown solutions into each of them. To one of the test tubes perform the sodium hydroxide(aq) test from stage 1 and note down your observations in a suitable table. To the second tube perform the ammonium hydroxide(aq) test from stage 1. In the remaining test tubes perform the various anion tests and again note down all positive and negative observations.

From your observations in stages 1 and 2 try to determine the composition of the solution and then repeat for the other unknown solutions.