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ANACHEM > MIDTERM > Flashcards

MIDTERM Flashcards

1
Q

The analytical results are free of errors or
uncertainties.

A

impossible

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2
Q

Minimize these errors and estimate their size with
acceptable accuracy.

A

Possible

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3
Q

use to judge the quality of
experimental measurements are many

A

statistical calculations

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4
Q

Chemists usually carry ______ through an entire
analytical procedure

A

two to
five portions (replicates) of a
sample

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5
Q

are synonyms for the quantity
obtained by dividing the sum of replicate measurements by the number of
measurements in the set:

A

Mean, arithmetic mean, and average (x ̄ )

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6
Q

is the middle result when replicate data
are arranged in order of size

A

median

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7
Q

For an odd number of data points, the median can
be

A

evaluated directly

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8
Q

For an even number, the mean

A

mean
of the middle pair is used

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9
Q

describes the reproducibility of
measurements; the closeness of results to each
other .

A

Precision

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10
Q

is determined by repeating the
measurement on replicate samples.

A

Precision

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11
Q

Three terms to describe the precision of a set
of replicate data:

A

standard deviation, variance,
and coefficient of variation

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12
Q

is a function of the deviation from
the mean di, or just the deviation

A

Precision

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13
Q

is the closeness of results to others
that have been obtained in exactly the same
way

A

Precision

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14
Q

indicates the closeness of the
measurement to its true or accepted
value and is expressed by the error

A

Accuracy

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15
Q

measures agreement
between a result and its true value

A

Accuracy

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16
Q

Relative error is also expressed in

A

parts per
thousand (ppt)

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17
Q

in statistics, a finite number of experimental
observations is called a

A

sample of data

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18
Q

Statisticians call the theoretical infinite number of
data a

A

population, more specifically a parent
population, or a universe, of data

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19
Q

must be modified substantially
when applied to a small sample because a few
data points may not be representative of the
population

A

Statistical laws

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20
Q

is a measure of the precision or scatter of a
population of data, which is given by the equation

A

σ or population standard deviation

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21
Q

the number of data points making up
the population.

A

N

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22
Q

The square of the standard deviation σ2

A

variance

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23
Q

quantity N — 1 is called the

A

number of degrees
of freedom

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24
Q

People who do scientific work tend to use ——— rather than variance as a measure of precision.

A

standard deviation

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25
Q

Another term to describe the precision of a set of
replicate results.

A

Spread or Range (w)

26
Q

It is the difference between the largest value in the
set and the smallest.

A

Spread or Range (w)

27
Q

Defining a numerical interval around the mean of a set of
replicate analytical results within which the population
mean can be expected to lie with a certain probability.
This interval is called the

A

confidence interval

28
Q

define a numerical interval
around that contains μ with a certain probability.

A

Confidence limits

29
Q

the numerical
magnitude of the confidence limit.

A

confidence interval

30
Q

Individual results from a set of
measurements are seldom the
same so a ______ is used for the set.

A

central or “best”
value

31
Q

represents the individual values of x making
up a set of N replicate measurements

A

Xi

32
Q

Three terms to describe the precision of a set
of replicate data:

A

standard deviation, variance,
and coefficient of variation.

33
Q

E in the measurement of a
quantity xi is given by the equation:
• where xt is the true, or accepted, value of the
quantity.
• Note that we retain the sign in stating the error .

A

Absolute Error

34
Q

is a more useful
quantity than the absolute error

A

relative error Er

35
Q

the difference between x and μ decreases rapidly

A

N
reaches over 20 to 30.

36
Q

People who do scientific work tend to use ____ rather than variance as a measure of precision.

A

use standard
deviation

37
Q

defined as the mass relationships
among reacting chemical species.

A

Stoichiometry

38
Q

gives the simplest whole-number
ratio of atoms in a chemical compound.

A

empirical formula

39
Q

_______ specifies the number of atoms in a
molecule.

A

molecular formula

40
Q

two or more substances may have the same empirical
formula but

A

different molecular formulas

41
Q

is obtained from the percent composition of a
compound.

A

empirical formula

42
Q

requires a knowledge of the molar
mass of the species.

A

molecular formula

43
Q

provides additional information

A

structural formula

44
Q

is a statement of the combining
ratios, or stoichiometry (in units of moles), among the reacting
substances and their products.

A

balanced chemical equation

45
Q

This reactant limits the chemical reaction

A

Limiting reactant

46
Q

Limiting Reactant is also called

A

limiting reagent

47
Q

It is completely used up in the reaction, and thus
determines when the reaction stops

A

Limiting Reactant

48
Q

Most of the solutes we discuss are electrolytes, which
form ______ when dissolved in water (or certain other
solvents) and thus produce solutions that conduct
electricity.

A

ions

49
Q

in a _____, strong electrolytes ionize essentially
completely, whereas weak electrolytes ionize only
partially.

A

solvent

50
Q

Based on ________ , an acid is a proton donor and base is
a proton acceptor .

A

Bronsted-Lowry theory

51
Q

acid is a _______ and base is
a _______ .

A

proton donor, proton acceptor

52
Q

species produced when an acid gives up a proton is a potential proton acceptor called the ______ of the parent acid.

A

conjugate base

53
Q

is the product that is different from a base by one
proton.

A

Conjugate Acid

54
Q

Whenever a base accepts a proton,

A

an acid is formed.

55
Q

some species have both acidic and basic properties and are called

A

amphiprotic solutes

56
Q

behave as acids in the presence of basic solutes
and bases in the presence of acidic solutes.

A

Amphiprotic solvents

57
Q

react with water so completely that no
undissociated solute molecules remain.

A

strong acid

58
Q

which react incompletely with
water to give solutions that contain significant amounts of both
the parent acid and its conjugate base.

A

weak acid

59
Q

several acids are completely
dissociated and are thus of the same strength.

A

leveling solvent

60
Q

is defined as the mass relationships
among reacting chemical species

A

stoichiometry

ANACHEM (2 decks)

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