Chem 26 3rd LE Notes

7/25/2019 Chem 26 3rd LE Notes

1/18

Chem 26 Notes

UPDShould only be a supplement to discussions

Table of Contents*

Part 2 Introduction to nalytical

Chemistry

!" Introduction

!#" Stoichiometry!$" %olumetric nalysis

!#" Introduction

!2" cid&$ase Titration

!'" Precipitation Titration

!(" Comple)ometric Titration!" +edo) Titration

!C" Introduction to Potentiometry

!#" ,eneral Principles

!2" +eference -lectrode

!'" Indicator -lectrode!D" Introduction to bsorption

Spectroscopy

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!#" Interaction of +adiation and

.atter

!2" +adiation bsorption!'" Instrumentation

!-" Introduction to Separation

Techni/ues

!#" Separation by -)traction

!2" Chromato0raphic Separation!1" -/uations

*Ctrl 3 1 the roman numeral to s4ip to

that part5 -) !$5'"7

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!5#" Stoichiometry

Stoichiometry

brance regarding quantities

quantitative relationship of reactacts and products in reactions

mole/mass relationship in chemical reactions

Mole

Avogadro (6.0 ! "0#$

number of atoms% molecules% ions% etc in a given gram

&ravimetric Analysis

deals 'ith mass

compared 'ith olumetric

analyte

converted to insoluble ppt

isolated% and then 'eighed

used in ppt method

based on chemically related composition

Steps

)onvert

*solate

+eigh

, analyte

*f analyte is not precipitate

but chemically related

mass and composition of related to analyte can lead to analyte

-!ample 'ould be a roc sample e1

#(gotten$ e (desired$

&ravimetric actor% &

for converting mass parameters

'here

n is determined by related/same elements

-!ample

Sulfur in S1#2S1

3

*ron in e#1

32e

1

#

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olatili4ation Method

quantitatively eliminate 'ater

direct

'ater collected over soliddessicant

calculate mass gain

indirect

loss mass after being heated calculate mass loss

Application

5etermine moisture

ractice

correct to a dry basis

compared to sample as received

add/remove 'ater to some reproducible level

-!ample7 "3.89, protein% "0.3, 'ater% etc

-quation

'here

:M is non volatile matter

roteins is the compound desired

:ote

:onvolatile Matter ; 5ry

+ater ; olatile

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!$5#" Introduction

olumetric ac

for slo' reactions

use e!cess to speed up reaction

amount of e!cess used to react 'ith analyte is determined by titration 'ith ndstandardi4ed solution

5isplacement

)omple!ometric

-5


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!$52" cid&$ase Titration

Acid2>ase

:eutrali4ation @eaction

== 12 1

fast

'hich is ideal

Ktitrant

; "/ "!"02"3

*ndicators

change in color% etc

produces observable physical change at/near eq. pt.

natural or synthetic

+ea organic acid/base that differs in color from conBugate base/acid

change color at a certain p

determine p it changes at

*deally% C*nD ; C*n2D

if C*nD 'ere yello' and C*n2D 'ere red% then solution 'ould be orange

5etermine p of solution

at equivalence point

p ; pKa

ideally% if p ; 8% indicator pKa ; 8

)olor

ull acid color ; pKa = "

ull base color ; pKa ? "

-!ample

if Ka; "!"023

Acid color p ; #

>ase color p ; 8

)omplete change in color from # to 8

p range ; 3 E "

@eaction should occur bet'een # and 8

Application

construct graph

@egions in )urve

*nitial oint

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olume ; 0

re2equivalence oint

p determined by !Fs =/12

olume G -q oint

-quivalence oint

p is dissociation of 1

ost -quivalence

p determined by !Fs titrant

olume H -q oint

+ea >ase ? Strong Acid

opposite graph of Strong >ase ? +ea Acid

use Kb

and related enderson 2 asselbalch equation

ase 2 Strong Acid

best change in p at equivalence point steep curve

if Ka ; "02I

titrationg is no longer feasible

high error% curve not steep enough

"026is the cutoff% though deliado pa rin

5etermine appropriate indicator

-asily pinpoint eq pt or p at eq pt

KBeldahl Method

determine organic nitrogen

protein analysis

fertili4er

Steps

Sample (>ound :$

= )onc S1

3% J

:3

=

= !Fs Strong Acid

:#% liberated

= >ac titrated 'ith standardi4ed base

Soda Ash

double indicator

lie in lab

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!$5'" Precipitation Titration

recipitation


9/18

5)2= )l2 :@

Ag)l is a coloid% Ag)lO)l2! 5)2

-nd point is Ag)lOAg=5)2

:ame


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!$5(" Comple)ometric Titration

)omple! ormation


11/18

!$5" +edo) Titration

@edo!


12/18

stronger the e

ses

)opper

ero!ide

14one

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!C5#" ,eneral Principles

otentiometry

arts

@eference -lectrode

-ref

Salt >ridge

-B

Analyte Solution

*ndicator -lectrode

-ind

-quation

-cell ; -in ? -ref = -B

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!C52" +eference -lectrode

@eference -lectrode

accureately no'n

independent of concentration

anode

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!C5'" Indicator -lectrode

*ndicator -lectrode

ighly specific

potential depends on activity% concentration

)athode

)alomel

S)-

g/g% )l

%

Silver/ Silver )hloride

responds to change of analyte


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m; 0.08/n

*nert

carbon%etc

Membrane *ndicators

&lass

for p% sensitive

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!D5#" Interaction of +adiation and

.atter

Analytical )hemR

!D52" +adiation bsorption

Analytical )hemR

!D5'" Instrumentation

Analytical )hemR

!-5#" Separation by -)traction

Analytical )hemR

!-52" Chromato0raphic Separation

Analytical )hemR

!1" -/uations


18/18

KSev

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Chem 26 3rd LE Notes