Lecture Tools of analytical chemistry

Lecture 3
Tools of analytical chemistry


Volumetric
Volumetricflasks
flasksare
are
calibrated
to
contain
calibrated to contain
an
anaccurate
accuratevolume.
volume.
See
the
inside
See the insideback
back
cover
coverof
ofthe
thetext
textfor
for
tolerances
of
Class
tolerances of ClassAA

volumetric
volumetricglassware.
glassware.

Volumetric
Volumetricpipets
pipetsaccurately
accuratelydeliver
deliveraafixed
fixedvolume.
volume.
AAsmall
smallvolume
volumeremains
remainsin
inthe
thetip.
tip.

Volumetric flask.

Transfer or volumetric
pipets.

Measuring
pipets.

©Gary Christian,
Analytical Chemistry,
6th Ed. (Wiley)

Hamilton microliter syringe.


These
Thesesyringe
syringepipets
pipetscan
canreproducibly
reproduciblydeliver
deliveraaselected
selectedvolume.
volume.
They
Theycome
comein
infixed
fixedand
andvariable
variablevolumes.
volumes. The
Theplastic
plastictips
tipsare
aredisposable.
disposable.

Fig. 2.12 Single-channel and multichannel
digital
displacement pipets and microwell plates.

©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley)


AA50-mL
50-mLburet
buretisismarked
markedin
in0.1
0.1mL
mLincrements.
increments.
You
Youinterpolate
interpolateto
to0.01
0.01mL,
mL,good
goodto
toabout
about±0.02
±0.02mL.
mL.
Two
Tworeadings
readingsare
aretaken
takenfor
forevery
everyvolume

volumemeasurement.
measurement.

Typical buret.


 How to read the markings of glassware?

 How to read the liquid level?
 How to clean glassware?


How to prepare solutions?
Stock solutions:
 Weigh (or measure an appropriate volume for liquid)
 Dissolve
 Bring to desired volume

 Preparing solutions by dilution:
- Co is the stock solution’s concentration
- Vo is the volume of stock solution being diluted
- Cd is the dilute solution’s concentration
- Vd is the volume of the dilute solution.


 Whats’ the volume of 1000 ppm stock solution of Cu2+
needed to prepare 100 mL of 15 ppm solution of Cu 2+?
 C0V0 = CdVd
 1000ppm x V0 = 15ppmx100 mL
  V0 = 1.5 mL

Problems
A) A laboratory procedure calls for 250 mL of an
approximately 0.10 M solution of H2C2O4. Describe how you
would prepare this solution using solid H2C2O4•2H2O.
B) A laboratory procedure calls for 250 mL of an approximately
0.10 M solution of HCl. Describe how you would prepare this
solution using a stock solution of concentrated HCl (C% =
37.5%; d = 1.19 g/ml).


Homework
1

2)

a) What is the concentration (expressed as mol/L = M) of NaCl
when 32.0 g of NaCl is dissolved in water and diluted to 0.500 L?

b) How many grams of methanol (CH3OH, formula weight =
32.04) are contained in 0.100 L of 1.71 M aqueous methanol?

c) Any dilute aqueous solution has a density near 1.00 g/mL.
Suppose the solution contains 1 ppm of solute; express the
concentration of solute in g/L, mg/L, g/mL and mg/mL.
3) Problem 4, Chapter 2, Harvey’s text book.
4) Read Chapter 4. Characterisation of data * sources of errors, how to
eliminate errors.* The importance of stastical analysis, Gaussian
distribution vs. t-distribution.