E relative
(|x1-x(true)|)/x(true) *100
standard deviation
sqrt((x1-x)^(2)+(x2-x)^(2))/(n-1)
relative standard deviation
(s/x(mean))*100
relative uncertainty
(abs uncertainty)/measured value
How are vol pipets calibrated?
For last drop to not be forced out
TC
to contain
TD
to deliver
Tolerance
max permissible deviation of measured value
propagation of uncertainty add or sub
sqrt(x^(2)+x2^(2)......)
propagation on uncertainty multiplication or subtraction
sqrt((x/a)^(2)+(x/b)^(2))
for gaussian curve +2 sigma is....
68.2%
for gaussian curve what is +3 sigma....
99.7%
Qcalc
(gap)/(range)
Grubbs test
|mean-poss outlier|/s
uncertainty
mu=mean+/- ts/SQrt(N)
S pooled
sqrt((Na-1)sa^(2)+(Nb-1)sb^(2))/(Na+Nb-2)
tcalc
Least sq method
The best fit line through a set of data points in which the line which min the sum of sq of
deviations between data points and lines.
linear range
conc range of analyte over which linear detector is linearly proportional
Sensativity
slope of linear portion of a/b curve
min det limit
, 3s/m
lim of quant
10s/m
internal calibration
carried out through the method of standard additions. Known analyte.
method of standard additions
accounts for matrix effects. Calibration occurs within the sample matrix
multi-point standard addition
4-5 id clean and dry vol flasks obtained. Volume of sample added to each flask. Next
variable amounts of standard solution spiked in each flask.
Requirements of Internal standard
1. Must produce a response easily distinguishable from analyte
2. Should be chemically similar
3. should be chemically stable
equilibrium point
when analyte is consumed by reaction
direct titration
when all the titration is added till all the analyte is consumed by reaction
back titration
analyst prep adds a known quantity of standard reagent in excess to consume all
analyte, then titrated back to eq
endpoint
the point in a titration where the indicator changes color
requirements of primary standards
1. Should be stable
2. should not be hydroscopic
3. should be stable when heated
4. high molecular weight
molamity
moles of sol/ kg of sol
common ion
suppresses dissulation
bronsted lowry acids
donate protons
Brinsted-Lowry base
accept protons
Ka=kw/kb
Ka rules
1. Ka1 will always be bigger than Ka2
2. The inc in H from first proton donation supplies further reaction donation
3. The conc of the int form is lower than the conc of the fully protanted form
Buffers
are solutions that resist change in pH when a small amount of acid or base is added.
Are always composed of a weak acid and conj base.
Buffer capacity
limit to which buffer is able to resist change
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