Assignment: Introduction to Qualitative Analysis

Purpose

The purpose of this experiment is to (1) perform a series of control experiments for the interaction of silver, lead (II), nickel, barium, and iron (Ill) ions with various reagents, and (2) create a flow chart illustrating the confirmatory tests for the analysis of an unknown sample containing one or more of the above listed cations.

Introduction

Qualitative Analysis is a process used to identify whether certain substances are present in a solid or solution. When performing qualitative analysis, the experiment deals only with whether a substance is present or not. On the other hand, quantitative analysis is a determination of the quantitity of the substance present. Qualitative analysis is done by determining the presence (or absence) of a substance based on how the ions react to different reagents. A reagent is a solution that has the potential to react with one or more ions in a solution, often producing visible evidence of a chemical reaction. The following indications of a chemical reaction are commonly seen upon the addition of reagents:

1. The formation of a precipitate
2. A change in color of the solution and/or texture of a solution
3. Re-dissolving of a precipitate through the addition of heat
4. Evolution of a gas

Pre-Lab Questions

Read the Appendix entitled "Operation of a Centrifuge" and answer the following questions.

1. Why is it important to balance the centrifuge before using it?
2. How do you properly balance a centrifuge if an odd number of samples must be centrifuged?
3. Why is it important NOT to stop the centrifuge abruptly?
4. Given the following reaction:

Hg(NO₃)₂ (aq) + 2HCI (aq) → Hg₂Cl₂ (s) + 2HNO₃ (aq)

Which compound would be present as a precipitate, and which one would be present in the supernatant?

Part 2: Analysis of an Unknown Sample

Using the flow chart created based on experimental data from Part 1, analyze an unknown containing one or more of the tested ions. In Data Table 2, record the unknown number of the sample sample tested and the ions present within the sample. In addition, record any observations that lead to the conclusion of an ion being present/not present within the unknown sample.

Attachment:- Lab-Assignment.pdf