Concentrations Molarity Dilutions

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Prelab Concentrations, Molarity, Dilutions

PDF - Concentration, Molarity, Dilutions

Purpose

To introduce the concepts of concentration, molarity, dilution and spectrophotometry (absorption spectra, standard curve, and Beers Law).

Introduction

Color is an important factor in our choice of food. It can affect how we perceive flavor and how likely a product is to catch our eye. Food and drink manufacturers are aware of color’s potential and often add dyes to their products to make them more appealing. Nitrates are added to meats to keep them bright red, sulfites are added to dried fruits to preserve their color, dyes are added to beverages to give them their characteristic look and indicate flavor. To a chemist, color can be a source of information.

In order for something to be colored, it must absorb (or sometimes scatter) some wavelengths of light more than others. How a chemical absorbs light depends on how that light interacts with its electrons; interaction with electrons is the central idea of chemistry. Qualitatively, color can tell us if a solution is acidic or basic, it can announce a chemical reaction or we can use it to detect the presence of a substance like iron in our water or starch in food. With the help of an instrument called a spectrophotometer, color can do even more. It can identify solutes and allow us to determine their concentration in solution.