Exam 1

Question 1

weighing by mass used for…

Answer 1

hygroscopic reagents

Question 2

TC

Answer 2

to contain

Question 3

TD

Answer 3

to deliver

Question 4

sample

Answer 4

a representative portion of the material of interest

Question 5

matrix

Answer 5

everything in the sample

Question 6

analyte

Answer 6

component of interest in the sample

Question 7

trace amount

Answer 7

ppb or <0.01%

Question 8

minor component amount

Answer 8

ppt or 0.01-1%

Question 9

major component amount

Answer 9

pph or >1%

Question 10

defining replicates

Answer 10

dividing into aliquots

Question 11

classical wet methods

Answer 11

gravimetric
titration

Question 12

instrumental methods

Answer 12

separation techniques
spectroscopy
electrochemical

Question 13

classical methods based on…

requires…

Answer 13

mass & volume, chemical properties

well-defined rxn stoichiometry

Question 14

instrumental methods based on…

Answer 14

signals generated by the analyte with an instrument

Question 15

relationship between signal and concentration in instrumental methods

Answer 15

s = kC

k is a constant

Question 16

screening assay

Answer 16

determines what exists in a sample

Question 17

information provided by analytical chemistry

Answer 17

qualitative

quantitative

chemical identification

structural analysis

property characterization

spatial analysis

time-dependent analysis

Question 18

formal concentration (F)

Answer 18

molarity of a strong electrolyte

Question 19

molality

Answer 19

moles of solute / kg of solvent

Question 20

advantage of molality vs molarity

Answer 20

molality does not depent on temperature

Question 21

ppm =

Answer 21

(mass substance / mass sample)10^6

mg/L (density @1 g/mL)

mg/kg

μg/g

ng/mg

Question 22

ppb =

Answer 22

(mass substance / mass sample)10^9

μg/L (density @ 1 g/mL)

μg/kg

Question 23

if K > 1….

Answer 23

forward rxn is favored

Question 24

define significant figures

Answer 24

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

Question 25

sig fig rules for addition and subtraction

Answer 25

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

Question 26

sig fig rules for multiplication and division

Answer 26

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

Question 27

sig fig rules for logarithm-generated numbers

Answer 27

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

Question 28

analytical concentration

Answer 28

does not consider what happens to solute after dissolution

Question 29

species concentration

Answer 29

considers chemical changes to solutes

Question 30

specific gravity

Answer 30

Dsoln / 1 g/mL = SG (no units) ratio of denisty of soln to density of H2O @ 4° C

Question 31

purity grades in order from least to greatest purity

Answer 31

technical/lab grade certified ACS & USP, BP, EP, NF, FCC grade biotech grade HPLC grade trace metal grade

Question 32

advantage of using stock soln

Answer 32

allows use of larger solute masses - less relative uncertainty

Question 33

define p function

Answer 33

pX = -log(X)

Question 34

2 types of error

Answer 34

systematic (determinate) random (indeterminate)

Question 35

detection of systematic error

Answer 35

multiple checks with multiple analysts test a known/blank standard unusual trends use of different analytical methods

Question 36

accuracy

Answer 36

difference between experimental value and true value

Question 37

precision

Answer 37

variation in experimental results

Question 38

absolute error (e) =

Answer 38

e = x - μ x = experimental result μ = true value

Question 39

relative error (eR) =

Answer 39

eR = e/μ e = absolute error μ = true value

Question 40

standard deviation describes...

Answer 40

precision

Question 41

variance =

Answer 41

s^2

Question 42

relative standard deviation (ppt) =

Answer 42

RSD = s/x(1000)

Question 43

good, mediocre, bad RSD for classical wet methods

Answer 43

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

Question 44

good RSD for instrumental methods

Answer 44

<10

Question 45

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

Answer 45

68

Question 46

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

Answer 46

95

Question 47

why does increasing n make x more accurate?

Answer 47

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

Question 48

relative error =

Answer 48

sy / y

Question 49

CI =

Answer 49

x ± (ts) / √n

Question 50

CI represents...

Answer 50

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

Question 51

criteria for suspicion of data points

Answer 51

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

Question 52

2 tests for outliers

Answer 52

Dixon (Q) Grubbs (Tn)

Question 53

Q =

Answer 53

|xo - xn| / xhigh - xlow xn = nearest value to outlier

Question 54

Tn =

Answer 54

|xo - x| / s

Question 55

steps to make a solution

Answer 55

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

Question 56

null hypothesis

Answer 56

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

Question 57

purpose of student's t test

Answer 57

tests accuracy of method with a known standard

Question 58

t = |x - μ| / (s / √n) μ = reference value

Answer 58

student's t test

Question 59

purpose of F test

Answer 59

comparison of precisions between 2 data sets

Question 60

purpose of s pool test

Answer 60

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

Question 61

purpose of tcalc test

Answer 61

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

Question 62

coefficient correlation (r) describes...

Answer 62

how well the data points fit a linear regression

Question 63

if r = 1... if r is high... if r is low...

Answer 63

r = 1; line fit is perfect high r; more confidence low r; more scattering of data points

Question 64

used to determine if a data set is linear

Answer 64

residual plot

Question 65

in a residual plot, true linear plots have data...

Answer 65

scattered around 0

Question 66

purpose of calibration curve

Answer 66

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