Analytical Chemistry Chapter 1 Flashcards
Measurement science consisting of a set of powerful ideas and methods that
are useful in all fields of science, engineering, and medicine
Analytical Chemistry
Establishes the chemical identity of the
species in the sample
Qualitative Analysis
Determines the relative amounts of these species, or analytes, in numerical terms.
Quantitative Analysis
An integral part of the separation step.
Qualitative Analysis
Essential adjunct to quantitative analysis.
Determining the identity of the
analytes
Are the components of a
sample that are determined.
The substance being determined.
Analytes
What is the role of Analytical Chemistry?
It is applied throughout industry, medicine, and all the sciences.
Give Example of Role of Analytical Chemistry
Conc. of Oxygen and carbon dioxide - treat illnesses.
Hydrocarbons, nitrogen oxides, and carbon monoxide - emission-control devices in automobile.
Ionized calcium - parathyroid disease.
Quantitative determination of nitrogen in foods - protein content and nutritional value.
Analysis of steel - adjustment in
the concentrations of such elements as carbon, nickel, and chromium to achieve
a desired strength, hardness, corrosion resistance, and ductility.
The mercaptan content of household gas - odor to warn of dangerous leaks.
Farmers tailor fertilization and irrigation - plant needs,, gauging these needs from quantitative analyses of plants and soil.
Play a vital role in many research areas in chemistry, biochemistry, biology, geology, physics, and the other sciences.
Quantitative analytical measurements
Archaeologists identify the sources of volcanic
glasses (obsidian) by___________ in samples taken from various locations.
Measuring concentrations of minor elements
Draw the figure 1-1. The relationship between analytical chemistry, other branches of chemistry, and the other sciences.
Often called the central science; its top-center position and the central position of analytical chemistry in the figure emphasize this importance.
Chemistry
What makes a chemical analysis a vital tool in medical, industrial, government, and
academic laboratories throughout the world.
The interdisciplinary nature of chemical analysis.
Enumerate the Quantitative Analytical Methods
Gravimetric methods
Volumetric method
Electroanalytical methods Spectroscopic methods
Determine the mass of the
analyte or some compound chemically related to it
Gravimetric Methods
Measures the volume of a solution containing sufficient reagent to react completely with the analyte.
Volumetric Method
Measure electrical properties such as potential,
current, resistance, and quantity of electrical charge
Electroanalytical Methods
Explore the interaction between electromagnetic radiation and analyte atoms or molecules or
the emission of radiation by analytes
Spectroscopic Methods
In a group of miscellaneous methods, what do we measure?
we measure such quantities as:
mass spectrometry
rate of radioactive decay
heat of reaction
rate of reaction
sample thermal conductivity
optical activity
refractive index
Draw figure 1-2, steps in quantitative analysis
The essential first step in any quantitative analysis is the____
selection of a method
One of the first questions that must be considered in the selection process
is the_________.
level of accuracy required
A second consideration related to economic factors is the____
number of samples that
will be analyzed
What influence the choice of method to some degree in quantitative analysis?
Finally, the complexity of the sample and the number of components in the sample
the second step in a quantitative analysis is to
acquire the sample
A material is __________if its constituent parts can be
distinguished visually or with the aid of a microscope. Coal, animal tissue, and soil are heterogeneous.
heterogeneous
An ________ is the process of
determining how much of a given sample is the material by its indicated name. e. For example, a zinc alloy is assayed for its zinc content, and its
_______ is a particular numerical value.
assay
Is the process of collecting a small mass of a material whose composition accurately represents the bulk of the material being sampled.
Sampling
the third step in an analysis is to_______
process the sample
Under most circumstances,
the sample is processed in one of the several different ways. The first step in processing the sample is often the __________
preparation of a laboratory sample
In preparing a laboratory sample:
A solid laboratory sample is _____ to decrease particle size, _______ to ensure homogeneity, and ______ for various lengths of time before analysis begins.
_________ of water may occur during each step, depending on the humidity of the
environment. Because any loss or gain of water changes the chemical composition of
solids, it is a good idea to _______ samples just before starting an analysis.
Alternatively, the moisture content of the sample can be determined at the time of the analysis by a ________.
Liquid samples present a slightly different but related set of problems during the
preparation step. If such samples are allowed to stand in open containers, the solvent
may __________.
If the analyte is a gas
dissolved in a liquid, as in our blood gas example, the sample container must be
kept inside a ________, perhaps during the entire analytical procedure, to prevent contamination by atmospheric gases.
may be required to preserve the integrity of the sample.
ground, mix, stored
absorption/desorption
dry
separate analytical procedure
evaporate and change the concentration of the analyte
second sealed container
sample manipulation and measurement in an inert atmosphere
Preparing Solutions: Physical and Chemical Changes
Because many classical methods and most instrumental techniques use solution samples, most analyses are performed on solutions of the sample made with a suitable ________
Unfortunately, many materials that must be analyzed are insoluble in common solvents. Examples include:______
________Is often the most difficult and time-consuming task in the analytical process.
The sample may require heating with_____________
It may be necessary to ignite the sample in _________ of the sample in the presence of various fluxes.
Is a material, often an
alkali metal salt, that is mixed
with the sample and heated to
form a fused salt.
solvent
silicate minerals, high-molecular-mass polymers, and specimens of animal tissue.
Converting the analyte into a soluble form
aqueous solutions of strong acids, strong bases, oxidizing agents, reducing agents, or some combination of such reagents.
air or oxygen or to perform a high-temperature fusion
Flux
In defining replicate samples
Most chemical analyses are performed on replicate samples whose masses or volumes have been determined by careful measurements with an ________.
Improves the quality of the results and provides a measure of their reliability.
Are portions of a material of
approximately the same size that are carried through an analytical procedure at the same time and in the same way
analytical balance or
with a precise volumetric device
Replication
Replicate samples, or replicates
Calibrating and Measuring Concentration:
Formula:
Stands for:
cA
k
X
The process of determining k is thus an important step in most analyses; this step is _________
Process of determining the proportionality between analyte concentration and a measured quantity.
Is the collection of all the components in the sample containing an analyte.
Techniques or reactions that work for only one analyte are said to be _______. Techniques or reactions that apply to only a few analytes are _______.
cA = kX
cA- Concentration of the analyte
k- proportionality constant
X - final measurement of a physical or chemical property of the analyte
Calibration
matrix, or sample matrix
specific
selective
In Eliminating Interferences:
Once we have the sample in solution and converted the analyte to an appropriate
form for measurement, the next step is to ___________
Few chemical or physical properties of importance in chemical analysis are unique to a single chemical species. Instead, the reactions used and the properties measured are ___________.
Species other than the analyte that affect the final measurement are called ______
species that causes an error in an analysis by enhancing or attenuating (making smaller) the quantity being measured.
eliminate substances from the sample that may interfere with measurement
characteristic of a group of
elements of compounds
interferences, or interferents
Calculating Results
Computing ______ from experimental data is usually relatively easy, particularly with computers.
This step is depicted in the next-to-last block of the
flow diagram of Figure 1-2.
These computations are based on the________________
analyte concentrations
calculate results
- Raw experimental
data collected in the measurement step - Characteristics of the measurement instruments
- Stoichiometry of the analytical reaction.
Evaluating Results by Estimating Reliability
analytical results are complete only when their _______.
reliability has been estimated
Process of continuous measurement and control is often referred to as a _______,
Cycle of measurement, comparison, and control is called a__________.
Draw figure 1-3
feedback system
feedback loop
Scientists throughout the world have adopted a standardized system of units known
as the_____________
International System of Units (SI)
is an unchanging measure of the quantity of matter.
is the force of gravitational attraction
between that matter and Earth
Mass m
Weight w
The SI unit for the amount of a chemical substance.
It is always associated with specific microscopic entities such as atoms, molecules,
ions, electrons, other particles, or specified groups of such particles as represented by a
chemical formula
mole
The fixed number 6.02214076 x 1023 is known as
Avogadro’s constant
The ______ of a substance is the mass in grams of 1 mole of that substance.
The molar mass M
Is the closeness of results to others obtained in exactly the same way.
Precision
Is the closeness of a
measured value to the true or
accepted value.
Accuracy
The_________ of a
measurement is the difference
between the measured value and the true value.
The sign of the absolute error tells you whether the value in question is high or low.
If the measurement result is low, the sign is ______; if the measurement result is high, the sign is _________.
absolute error
negative
positive
The _______ of a measurement
is the absolute error divided by
the true value.
relative error
Types of Errors in Experimental Data
Causes data to be scattered more or less symmetrically around a mean value.
affect measurement precision.
They arise from experimental
variables that cannot be controlled or determined. Examples include: random fluctuations in electrical
noise, random inconsistencies in measurement readings, or random changes in laboratory temperature
random (or indeterminate) error
causes the mean
of a data set to differ from the accepted value.
These errors often occur when instruments or measuring devices are uncalibrated
or are calibrated improperly. They have the same effect on all samples. Systematic errors can be very subtle and difficult to detect, but finding and eliminating them is an integral
part of the measurement process.
systematic (or determinate) error
Occur infrequently and
often result from an experimental
blunder such as misreading a scale or
interpreting a number incorrectly
They usually occur only occasionally, are often large, and may
cause a result to be either high or low. They are often the product of human errors.
Gross errors
