First Exam

Question 1

This is the most common method for expressing the
concentration of a solution in biochemical studies.

Answer 1

Molarity

Question 2

is one that contains a
precisely known concentration of solute.

Answer 2

Standard Solutions

Question 3

is the one having
a concentration many folds higher than that actually required in
the experiment.

Answer 3

Stock Solutions

Question 4

A solution which contains mole of the solute dissolved in 1 kg of
the solvent is called a molal solution.

Answer 4

Molality

Question 5

expresses concentration in terms of the equivalents
of one chemical species reacting stoichiometrically with
another chemical species; a function of chemical reaction.

Answer 5

Normality

Question 6

is the number of gram equivalents
of the solute per litre of the solution.

Answer 6

Normality

Question 7

This is generally employed for those solutions in which a
substance is present in a very small quantity.

Answer 7

ppm or ppb

Question 8

a measurement science consisting of a set of powerful ideas and
methods that are helpful in all fields of science and medicine

Answer 8

analytical chemistry

Question 9

concerned with the chemical characterization of matter;

Answer 9

analytical chemistry

Question 10

concerned with the theory and practice of methods used to
determine the composition of matter;

Answer 10

Analytical chemistry

Question 11

involves separating, identifying and determining the relative
amounts of the components in a sample of matter.

Answer 11

analytical chemistry

Question 12

is often called the central science

Answer 12

Chemistry

Question 13

data based on numbers

Answer 13

quantitative data

Question 14

data based on observations

Answer 14

qualitative data

Question 15

• deals with the identification of elements, ions or compound present in a sample.
• concerned with what elements or compounds is in the sample.
• reveals the chemical identity of a species in the sample.

Answer 15

Qualitative analysis

Question 16

• concerned with the determination of the amount of a particular substance present in a sample.
• establishes the relative amounts of one or more of these species or analytes.

Answer 16

Quantitative analysis

Question 17

Examples of wet chemical methods

Answer 17

precipitation, extraction, distillation, boiling
or melting points, gravimetric and
titrimetric measurements.

Question 18

Analytical measurements such as ——– are made using instrumentation

Answer 18

(conductivity, electrode potential, light absorption or
emission, mass-to-charge ratio,
fluorescence etc.)

Question 19

the mass of the analyte or some compound chemically
related to it is determined.

Answer 19

gravimetric method

Question 20

the volume of a solution containing sufficient reagent to
react completely with the analyte is measured.

Answer 20

volumetric method

Question 21

employs instruments other than those used in
gravimetric and volumetric methods of analysis.

Answer 21

instrumental methods

Question 22

involves the measurement of such electrical properties
as potential, current, resistance and quantity of electricity.

Answer 22

electroanalytical method

Question 23

examples of electroanalytical method

Answer 23

Potentiometry
Voltammetry
Coulometry

Question 24

based upon the measurement of the interactions between
electromagnetic radiation and the analyte atoms or molecules or
upon the production of such radiation by analytes.

Answer 24

spectroscopic method

Question 25

examples of spectroscopic method

Answer 25

• UV-VIS Spectroscopy • IR Spectroscopy • Atomic Absorption Spectroscopy (AAS) • Fluorescence Spectrophotometry • NMR Spectroscopy

Question 26

involves separation of sample components based on differences in their migration rates.

Answer 26

chromatographic method

Question 27

examples of chromatographic method

Answer 27

• Thin Layer Chromatography (TLC) • Gas Chromatography (GC) • High Performance Liquid Chromatography (HPLC)

Question 28

the classification of analyses are based on what 3?

Answer 28

Based on the extent of analysis Based on the size of the sample available for analysis Based on the type of constituents

Question 29

under the based on the extent of the analysis there are 3 types. what are they?

Answer 29

complete or exact ultimate proximate or partial

Question 30

Steps in a Typical Quantitative Analysis

Answer 30

Selecting a Method of Analysis Sampling Preparing a Laboratory Sample Defining Replicate Samples Preparing Solutions of the Samples Eliminating Interferences Calibration and Measurement of Concentration Calculating Results Evaluating Results by Estimating their Reliability

Question 31

what are the steps in an analytical process

Answer 31

sampling sample preparation chemical analysis calibration curves interpreting the results

Question 32

The analysis is meaningless unless:

Answer 32

⮚ you have collected the sample properly; ⮚ you have taken measures to ensure the reliability of the analytical method; ⮚ you communicate your results clearly and completely.

Question 33

The _______ is only the middle portion of a process that begins with a question and ends with a conclusion.

Answer 33

chemical analysis

Question 34

Chemists usually carry ________ replicates (portions) of a sample through an analytical procedure.

Answer 34

three to five

Question 35

___________ are samples of about the same size that are carried through an analysis in exactly the same way.

Answer 35

Replicates

Question 36

 arithmetic mean or average  the quantity obtained by dividing the sum of replicate measurements (xi) by the number of measurements (N) in the set.

Answer 36

mean

Question 37

 middle value of a sample of results arranged in order of increasing/decreasing magnitude.

Answer 37

Median

Question 38

 the value that occurs most frequently in a set of determinations.

Answer 38

Mode

Question 39

 describes the reproducibility of the measurements.

Answer 39

Precision

Question 40

 tells how close the results are, provided that they are obtained in exactly the same way.

Answer 40

precision

Question 41

 deals with repeatability (within-runs) and reproducibility (between-runs).

Answer 41

precision

Question 42

three terms are widely used to describe the precision of a set of replicate data:

Answer 42

standard deviation Variance coefficient of variation.

Question 43

indicates the closeness of the measurements to its true value or accepted value and is expressed by the error (or simply the proximity to the true value).

Answer 43

accuracy

Question 44

accuracy is expressed in terms of

Answer 44

a. absolute error, E =| xi- xt| b. relative error, Er = |xi- xt| / xi

Question 45

what are the 3 types of error

Answer 45

random/indeterminate systematic/determinate gross

Question 46

 causes data to be scattered more or less systematically around a mean value.  affect measurement precision

Answer 46

Random / Indeterminate Error

Question 47

 causes the mean of a set of data to differ from the accepted value.  causes the results in a series of replicate measurements to be all high or low.  e.g. loss of a volatile analyte while heating a sample.

Answer 47

Systematic / Determinate Error

Question 48

 occur only occasionally, are often large and may cause a result to be either high or low.  often the product of human errors.  e.g. precipitate is lost before weighing;  e.g. touching a weighing bottle with your fingers after its empty mass is determined.  leads to outliers, results that obviously differ significantly from the rest of the data of replicate measurements.

Answer 48

gross error

Question 49

Sources of systematic errors

Answer 49

instrumental method personal

Question 50

 caused by nonideal instrument behavior, by faulty calibrations, or by use under inappropriate conditions  caused by imperfection of measuring devices and instabilities in their power supplies.  e.g glasswares used at temperatures that differ from their calibration temperature  distortion of container walls, errors in the original calibration, contaminants on the inner surface of the containers  Calibration eliminates most systematic errors of this type.  Electronic instruments are also subject to systematic errors.  e.g. voltage of a battery- operated power supply decreases with use  e.g. instruments are not calibrated frequently or if they are calibrated incorrectly.  e.g. Temperature changes  Errors of these types are detectable and correctable.

Answer 50

instrumental error

Question 51

 arises from non-ideal chemical or physical behavior of analytical systems.  chemical or physical behavior of the reagents and reactions.  due to slowness of some reactions  incompleteness of a reaction  instability of some species  nonspecificity of the reagents  possible occurrence of side reactions

Answer 51

method error

Question 52

 arises from non-ideal chemical or physical behavior of analytical systems.  chemical or physical behavior of the reagents and reactions.  due to slowness of some reactions  incompleteness of a reaction  instability of some species  nonspecificity of the reagents  possible occurrence of side reactions

Answer 52

method error

Question 53

 results from the carelessness, inattention or personal limitations of the experimenter.  estimating the level of the liquid between two scale divisions  the color of the solution at the end point in a titration  level of a liquid with respect to a graduation in a pipet or buret

Answer 53

personal error

Question 54

Detection of Systematic Method Error:

Answer 54

a. analysis of standard samples b. independent analysis c. blank determination d. variation in sample size

Question 55

can be purchased from a number of governmental and industrial sources (e.g. National Institute of Standards and Technology, NIST which offers over 1300 SRMs)

Answer 55

Standard Reference Materials (SRM)

Question 56

Concentration of the SRM has been determined in one of the three ways:

Answer 56

1. through analysis by previously validated reference method, 2. through analysis by two or more independent, reliable measurement methods, 3. through analysis by a network of cooperating laboratories, technically competent and throughly knowledgeable with the material being tested.

Question 57

a second independent and reliable analytical method to be used in parallel with the method being evaluated. 🞑 should differ as much as possible from the method used. 🞑 This minimizes the possibility that some common factor in the sample has the same effect on both methods.

Answer 57

independent analysis

Question 58

a _______ contains the reagents and solvents used in a determination, but no analyte.

Answer 58

blank

Question 59

useful for detecting certain types of constant errors. all steps of the analysis are performed in the absence of the sample.

Answer 59

blank determination

Question 60

many of the sample constituents are added to simulate the analyte environment, which is called the _______ (collection of all the constituents in the sample).

Answer 60

sample matrix

Question 61

can detect constant errors (as the size of the measurement increases, the effect of a constant error decreases).

Answer 61

variation in sample size

Question 62

Statistical Treatment of Random Errors

Answer 62

sample population or universe population mean, μ sample mean

Question 63

a finite number of experimental observations; a tiny fraction of infinite number of observations; subset of measurements selected from the population.

Answer 63

sample

Question 64

the theoretical infinite number of data.

Answer 64

population

Question 65

true mean of the population; in the absence of any systematic error, this is also the true value for the measured quantity.

Answer 65

population mean

Question 66

the mean of a limited sample drawn from the population of the data

Answer 66

sample mean

Question 67

Measures of precision

Answer 67

pop std sample std std of the mean variance relative std coefficient of variation spread or range

Question 68

a measure of the precision of a population of data

Answer 68

pop std

Question 69

a measure of the precision of a sample of data

Answer 69

sample std

Question 70

the square of std

Answer 70

variance

Question 71

the difference between the largest value and the smallest in the set of data.

Answer 71

spread or range

Question 72

The exact value of the mean, μ, for a population of data can never be determined exactly because such a determination requires that an infinite number of measurements be made. Statistical theory, however, allows us to set limits around an experimentally determined mean within which the population mean lies with a given degree of probability. These limits are called _______, and the interval they define is known as the ________

Answer 72

confidence limits; confidence interval