chem 1

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chapter 1 title

Introduction to Analytical Chemistry

a body of procedures and techniques used to identify and quantify the chemical composition of a sample of a substance

chemical analysis

seeks to identify the substances in the sample, nature of a certain materials, appearance, color and odor...

qualitative analysis

attempt to determine the quantity or concentration of a specific substance in the sample, the proportion in which these constituents are present, it has to be measured.

quantitative analysis

sample determines the variation of color extraction aroma. precipitation, chromatography and spectroscopy

qualitative examination

Volume, density and specific gravity are also an example of

quantitative analysis

Two Aspects of Qualitative Analysis

Theoretical Aspects Experimental Aspects

is a continued study of the fundamentals of general chemistry. it is concerned with the study of electrolytes. The term electrolyte is used to identify a substance which is composed of ions or which produces ions in aqueous solutions. Example: Na Cl producing Na ions and Cl ions.

theorical aspects

the laboratory procedures are designed to identifying and determining the approximate amount of constituents present in a substance.

experimental aspect

is the most generally applicable of the separation methods and has many variants according to the nature of the column packing and the sample- constituent interaction

chromatography

The most important types of chromatography are

1 gel permeation chromatography Gas chromatography liquid liquid chromatography

in which large molecules separate according to their size; and ion exchange chromatography- in which charged, or ionic constituents are separated. -

gel permeation chromatography

separates the volatile constituents of a sample,

gas chromatography

separates small, neutral molecules in solution.

liquid liquid chromatography

the goal of separation

is to produce a purified or partly purified form of the desired constituent for analytical measurement, or to eliminate other constituents that would interfere with the measurement or both

when is separation is unnecessaey

unnecessary when the method is highly specific or selective and responds to the desired constituent while ignoring others

example of a measurement that does not require a separation step

measurint ph or hydrogen

Another step preparatory to both qualitative and quantitative analyses is????

standardization or calibration

is to develop and provide such standard samples.

National Institute of Standards and Technology

latter can be expressed as

weight percent, molar concentration moles of dissolved constituent per liter of solution), or ppm (parts per million by weight), Normality

The precision of the result is reflected by its

reproducibility, or repeatability.

Results from repeated measurements are called

precision

measurement tend to cancel one another out. Accuracy is nearly always improved by averaging multiple determinations. Depending on the method used, measurements may need to be repeated only three or four times.

random errors

in which computers are connected to the analytical instruments, as many as 100,000 measurements may be made very quickly. This technique is referred to as

signal averaging.

relies on certain chemical reactions to detect particular functional groups, such as alcohol, amine, aldehyde, olefin, ester, carboxylic acid, and ether (see Chemistry, Organic).

organic analysis

is used to identify a substance which is composed of ions or which produces ions in aqueous solutions.

electrolytes

vhemist are commonly analyzed such as

stainless material, beer, fingernail lz rose petal, smoke, aspirin and paper

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