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Unformatted text preview: Wm.wu———— CHEM 210
1 1/27/06 NAME: 1. (30 POINTS) (a) Suppose that you are using 0.050M NaOH to titrate a 25.00 ml
solution that contains an unknown mixture of H3P04 and HCl and that you obtain two
endpoints - the ﬁrst after adding 19.15 ml and the second after adding 17.85 ml more.
Calculate the molaﬁties of HCl and H3P04 in the unknown. SHOW YOUR WORK.
(Formula weights: N'aOI-I, 40.00 g/mole; HCl, 36.46 g/mole; H3P04, 98.00 g/mole) (b) Suppose that you notice that a fellow student titrating his/her unknown performs a similar titration but obtains only one endpoint. Even though you can’t see the endpoint
_ volume, what can you conclude about this unknown? 2. (24 POINTS) Match the following titration reactions with the plots that you would. i
expect each to exhibit: . m] titrant '95- o ’7 I
ml titrant ml'titrant 100
(e) (f) NONE OF THE ABOVE.
pH m'l titrant 05' I no 1) 25 ml of0.]0M BC] with 0.10M NaOH - '_
2) 50 ml of 0.10M NaOH with 0.20M HCl -
3) 25 ml of0.10M H3P04 with 0.10M HCl - 4) 25 ml of 0.10M Na2I—IPO4 with 0.10 M NaOH - 3. (20 POINTS) A buffer solution is one whose pH does not change very much even
when signiﬁcant amounts of acid or base are added to it. What two species must be" present in a buffer to allow it to resist such pH changes? Why? 4. (32 POINTS) (3) Outline, in block diagram form, the principal components of an
atomic absorption spectrometer (AAS). - . - rmmmﬂw mw—ﬂ-um—u—m
.-.--.—..— (b) What kinds of analytes is AAS well suited for? What kind of chemical information
samples does AAS not provide? - (c) What is Planck’s equation? What is meant by the term “quantization”? 5'. (24 POINTS) (a) Outline, in block diagram form, the principal components of a gas
chromatography (GC) instrument. 0’) 111 general: What kinds of analiztes is GC well suited for? For what kinds of samples is
GC not well suited? . . 6. (20 POINTS) Show clearly how you would prepare 200 ml of a 50 ppm K solution
from: a) a 200 ppm K stock solution. b) solid KC] (formula weight of KCl = 74.55 g/mOle; atomic weight of K = 39.10
g/mole; atomic weight of C1 = 35.45 g/mole). . mm_—.___ ...
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This note was uploaded on 09/12/2008 for the course CHEM 209 taught by Professor Greg during the Spring '07 term at University of Louisville.
- Spring '07