ChE 401 - Analytical Chemistry

Analytical chemistry for chemical engineering students.

Quantitative and qualitative analysis

Main divisions of analytical chemistry.

Qualitative analysis

Makes the elements and compounds in the sample identifiable and determines what materials are contained in a sample.

Quantitative analysis

Any method used for determining the amount of a chemical in a sample.

Solubility test

Used to determine if solid dissolves in the solvent.

Precipitation test

Used to see if solid formed when two dissolved substances mix.

pH test

Determine the concentration of dissolved [H] ions.

Flame test

Used to see what color is formed when the substance is burned.

Element/Molecular analysis

refers to the measurement of the amount of each element or molecule

Complete/Ultimate analysis

The total amount of constituents in the sample is determined.

Partial analysis

Only few constituents are determined.

Macro analysis

Implies that the constituent is in high concentration.

Trace analysis

Constituents to be determined are in low concentration.

Gravimetry

Uses the mass of the analyte or some compound related to it.

Volumetry

Also called titrimetry; measures the volume of the solution containing sufficient reagent to react completely with the analyte.

Electroanalytical

Involves the measurement of electrical properties such as potential, current, resistance, and quantity of electrical charge.

Spectroscopy

Based on the interaction of electromagnetic radiation with the analyte atoms or molecules, or by the analyte’s production of such radiation.

Miscellaneous groups of method

Measurements of such quantities such as mass-to-charge ratio of molecules by mass spectrometry, rate of radioactive decay, heat of reaction, thermal conductivity, optical activity, refractive index.

Analytical chemistry

A core set of operations and equipment that is necessary for laboratory work in the discipline and that serves as a foundation for its growth and development.

Reagent-grade

Chemicals range from 96 to 98 percent purity, or nearly ACS grade purity.

Primary standard-grade

The provider has thoroughly examined these reagents, and the assay is printed on the label of the container.

Secondary standard-grade

Purity has been established by chemical analysis and serves as reference material for titrimetric methods.

Special purpose reagent chemicals

Included among these are solvents for spectrophotometry and high-performance liquid chromatography.

modest cost

Give an important requirements of primary standard

Benzene and acetone

These are organic solvent effective in removing grease.

Marking ink

Available for porcelain surfaces. The marking is baked permanently into the glaze by heating at a high temperature.

Wet ashing

This is a process of adding sulfuric acid and heating to the appearance of sulfur trioxide fumes.

Analytical balance

A tool used to measure mass with a maximum capacity ranging from 1 gram to a few kilograms and precision of at least 1 part in 105 up to 106 at full capacity.

Buoyancy

When the things being weighed have a significantly different density than the masses, a weighing error occurs.

Temperature

A source of error in weighing, it is a large inaccuracy that occurs when an object’s temperature differs from its surroundings.

Static charge

A source of error in weighing, it is when a porcelain or glass object develops a static charge, especially in a low-humidity environment.

Weighing bottle

This is a simple tool for drying solids. A ground glass section of a cap-style is seen on the left, and as it is not in contact with the contents.

Desiccator

Dried materials are kept in here while cooling to reduce moisture absorption.

Simple crucible

These transform a precipitate into an appropriate weighing form at constant mass.

Filtering crucible

These act as both containers and filters. A vacuum is employed to speed up the filtration, and a variety of rubber adaptors can be used to create a tight seal.

Filter paper

It is a very important filtration medium. Ashless paper is used for igniting samples.

Low temperature drying

It runs between 1400°C and 260°C, with an acceptable drying temperature of 110°C.

Microwave laboratory ovens

Currently quite popular since it shortens drying cycles. It uses electromagnetic waves in the drying of the sample.

Ordinary heat lamp

Can be used to dry a precipitate that has been collected on ashless paper and to char the paper as well.

Burners

Practical place to get a lot of heat.

Meker

Provides the highest temperature.

Tirrill

For safe continuous stream of flammable gas.

Bunsen

Produces a single open gas flame.

Electric furnace

Capable of maintaining controlled temperatures of 1100°C or higher.

Pipette

These permit the transfer of accurately known volumes from one container to another.

Burette

Can achieve a degree of precision that is significantly higher than a pipette can. This is made up of valve system for controlling the flow of titrant and a calibrated tube to retain the titrant.

Volumetric flask

These are produced in sizes ranging from 5 mL to 5 L, and they are often calibrated to hold a particular volume when filled to a line etched on the neck.

Central value

Reliable than any of the individual results.

Analysis of variation

Allows us to estimate the uncertainty associated with the central result.

Mean

This is the most frequently employed central value indicator. The sum of replicate measurements is divided by the total number of measurements

Precision

This is the reproducibility of measurements or the similarity of outcomes.

Standard deviation and variance

Frequently used to characterize the precision of a collection of repeated data. These are based on the deviation from the mean.

Accuracy

The error, which expresses accuracy, shows how near a measurement is to the true or accepted value.

Absolute error

In the measurement of a quantity x is given by the equation.

Relative error

More useful quantity than the absolute error.

Error

The discrepancy between your response and the correct one.

Random or indeterminate error

Data are more or less symmetrically dispersed around a mean value as a result of error.

Systematic error

Data are more or less symmetrically dispersed around a mean value as a result of error.

Instrumental errors

Caused by non-ideal instrument behavior, by faulty calibrations, or by use under inappropriate conditions.

Method errors

Arise from non-ideal chemical or physical behavior of analytical systems.

Personal errors

Result from the carelessness, inattention, or personal limitations of the experimenter.

Gross error

The most common cause when utilizing an instrument is human error.