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CH271—Analytical Chemistry > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

weighing by mass used for…

A

hygroscopic reagents

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2
Q

TC

A

to contain

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3
Q

TD

A

to deliver

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4
Q

sample

A

a representative portion of the material of interest

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5
Q

matrix

A

everything in the sample

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6
Q

analyte

A

component of interest in the sample

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7
Q

trace amount

A

ppb or <0.01%

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8
Q

minor component amount

A

ppt or 0.01-1%

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9
Q

major component amount

A

pph or >1%

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10
Q

defining replicates

A

dividing into aliquots

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11
Q

classical wet methods

A

gravimetric
titration

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12
Q

instrumental methods

A

separation techniques
spectroscopy
electrochemical

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13
Q

classical methods based on…

requires…

A

mass & volume, chemical properties

well-defined rxn stoichiometry

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14
Q

instrumental methods based on…

A

signals generated by the analyte with an instrument

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15
Q

relationship between signal and concentration in instrumental methods

A

s = kC

k is a constant

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16
Q

screening assay

A

determines what exists in a sample

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17
Q

information provided by analytical chemistry

A

qualitative

quantitative

chemical identification

structural analysis

property characterization

spatial analysis

time-dependent analysis

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18
Q

formal concentration (F)

A

molarity of a strong electrolyte

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19
Q

molality

A

moles of solute / kg of solvent

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20
Q

advantage of molality vs molarity

A

molality does not depent on temperature

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21
Q

ppm =

A

(mass substance / mass sample)10^6

mg/L (density @1 g/mL)

mg/kg

μg/g

ng/mg

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22
Q

ppb =

A

(mass substance / mass sample)10^9

μg/L (density @ 1 g/mL)

μg/kg

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23
Q

if K > 1….

A

forward rxn is favored

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24
Q

define significant figures

A

total number of digits required to write a number in scientific notation without a loss in accuracy

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25
Q

sig fig rules for addition and subtraction

A

retain same number of decimal places of the number with the fewest

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26
Q

sig fig rules for multiplication and division

A

number with the greatest uncertainty determines sig figs of the product/quotient

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27
Q

sig fig rules for logarithm-generated numbers

A

only mantissa is significant, and includes 0 directly after decimal point

the number of sig figs in the number you are taking the log of determines the sig figs in the mantissa

28
Q

analytical concentration

A

does not consider what happens to solute after dissolution

29
Q

species concentration

A

considers chemical changes to solutes

30
Q

specific gravity

A

Dsoln / 1 g/mL = SG (no units)

ratio of denisty of soln to density of H2O @ 4° C

31
Q

purity grades in order from least to greatest purity

A

technical/lab grade

certified ACS & USP, BP, EP, NF, FCC grade

biotech grade

HPLC grade

trace metal grade

32
Q

advantage of using stock soln

A

allows use of larger solute masses - less relative uncertainty

33
Q

define p function

A

pX = -log(X)

34
Q

2 types of error

A

systematic (determinate)

random (indeterminate)

35
Q

detection of systematic error

A

multiple checks with multiple analysts

test a known/blank standard

unusual trends

use of different analytical methods

36
Q

accuracy

A

difference between experimental value and true value

37
Q

precision

A

variation in experimental results

38
Q

absolute error (e) =

A

e = x - μ

x = experimental result
μ = true value

39
Q

relative error (eR) =

A

eR = e/μ

e = absolute error
μ = true value

40
Q

standard deviation describes…

A

precision

41
Q

variance =

A

s^2

42
Q

relative standard deviation (ppt) =

A

RSD = s/x(1000)

43
Q

good, mediocre, bad RSD for classical wet methods

A

good: <4
mediocre: 4-10
bad: >10

44
Q

good RSD for instrumental methods

A

<10

45
Q

__% of measurements lie within +/-1 s of x

A

68

46
Q

___% of measurements lie within +/-2 s of x

A

95

47
Q

why does increasing n make x more accurate?

A

the more values there are, the more likely it is that (+) and (-) random errors cancel one another out

48
Q

relative error =

A

sy / y

49
Q

CI =

A

x ± (ts) / √n

50
Q

CI represents…

A

range around the mean, for a certain confidence level, within which the true value actually lies

51
Q

criteria for suspicion of data points

A

lies >±2 s of x
lies outside CI
seems suspicious based on experience

52
Q

2 tests for outliers

A

Dixon (Q)
Grubbs (Tn)

53
Q

Q =

A

|xo - xn| / xhigh - xlow

xn = nearest value to outlier

54
Q

Tn =

A

|xo - x| / s

55
Q

steps to make a solution

A
  1. transfer measured solute to flask
  2. dissolve in less than desired volume solvent and mix
  3. add more solvent, less than desired volume, and mix
  4. dilute to volume mark
  5. cap, mix and invert many times
56
Q

null hypothesis

A

that there is no difference between your result and the reference value

57
Q

purpose of student’s t test

A

tests accuracy of method with a known standard

58
Q

t = |x - μ| / (s / √n)

μ = reference value

A

student’s t test

59
Q

purpose of F test

A

comparison of precisions between 2 data sets

60
Q

purpose of s pool test

A

comparing the means of two data sets with similar precisions (via the F test)

61
Q

purpose of tcalc test

A

comparing the means of two data sets with dissimilar precisions (via the F test)

62
Q

coefficient correlation (r) describes…

A

how well the data points fit a linear regression

63
Q

if r = 1…
if r is high…
if r is low…

A

r = 1; line fit is perfect

high r; more confidence

low r; more scattering of data points

64
Q

used to determine if a data set is linear

A

residual plot

65
Q

in a residual plot, true linear plots have data…

A

scattered around 0

66
Q

purpose of calibration curve

A

use linear equation of a best-fit line to extrapolate x from y of an experimental value (or vice versa)

CH271—Analytical Chemistry (3 decks)

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