University:
Widener University
Course:
CHEM-101 | Intro to Chemistry I
Academic year:

2019
Views:

185

Pages:

1
Author:

esfredint7qo

General Analytical Techniques INTRODUCTION General Analytical Techniques INTRODUCTION Analytical chemistry enables us to identify the constituents of unknown compounds and the relative amounts of these constituents. When we identify an unknown compound, we are performing a qualitative analysis. On the other hand if we can numerically determine the amounts of constituents in an unknown sample, we are performing a quantitative analysis. For example, suppose you were asked to determine what had caused a large fish kill in a lake or river. You would first attempt to determine what is in the water to see what could have caused the disaster. This is qualitative analysis. Then you would determine how much of the suspected toxin was present to determine if the concentration was high enough to cause the problem. This is quantitative analysis. In this lab you will learn some of the techniques used in quantitative analysis. Quantitative analysis offers a numerical description of the amount of a constituent (the analyte) in a sample. In this lab we will express our measurements in molarity - moles of analyte per liter of solution. For your information you should be aware that often a more precise measurement is needed. When testing for toxicities, a thousandth of a gram can make the difference between a safe amount and one that is lethal. These measurements are often taken in parts per million, that is, one microliter of analyte per liter of sample! Over the next two weeks, you will have the opportunity to use two common analytical laboratory techniques. One of the procedures you will perform involves volumetric analysis using titration methods. You will need to prepare solutions of a specific concentration using volumetric glassware and graduated burets. In a volumetric analysis, you measure the volume of solution that contains a sufficient amount of reagent to react completely with the analyte. Another of the procedures you will perform involves spectroscopic analysis, using a GENESYSTM spectrophotometer. Using this method, you will need to focus on the proper preparation of aqueous solutions from solids and water, and on the process of diluting a concentrated solution. Some of these methods are more precise than others, but they will all be imprecise if your technique is poor. Try to be as accurate and as careful as possible. Also, be careful when using volumetric glassware as it is extremely expensive; handle all volumetric glassware with great care to avoid breakage. Before beginning the analytical experiments you should first become acquainted with common laboratory procedures. You must do this by reading the "Introduction" section of this manual. In addition, many of the calculations must be done before entering the laboratory. In doing these experiments you should keep in mind that the goal is to learn to make solutions properly, and to become acquainted with a couple of common analytical techniques. It is important to learn these procedures properly now so as to avoid costly errors later. You should also begin to understand that certain analytical techniques are more accurate than others.