m
a
Objectives:
INTRODUCTION
Colorimetry
6 indicator
! " " # $ $ " " "
6 indicator
%
" & " " "
6 indicator Indicator
Lower pH color
pH Range (transition interval)
Higher pH color
Thymol blue
a
' () ( *
+
Ýromophenol blue
+
, -) . /
0
Chlorophenol red
+
. *) / .
1
Ýromothymol blue
+
/ -) 2 /
3
Phenol red
+
/ *) * .
a
`cIlvainebuffersystem
3 $ 4 (0 .$ " !( (*#
Ýuffer solution
" %
"
% $ , 5
&
Common ion effect
6 0
" & $ "
Commonioneffect
& $ " $ " $ "
,
4 ,
Commonioneffect ,
5( , 5 5 ,
% 4 ,
4 5 5 ,
%
,
% 4 ,
$ " ,
6
7%"859
7%"8, 59
¬ciddissociationconstant,a
equilibrium !# ( " !%# , 5
78, 598%9 89
enderson-- asselbalchequation enderson
"
7 5"8 " 9 8 9
enderson-- asselbalchequation enderson
"
"
"
& " " ! 2#$ ! '" '#$ : ! '--'#
m mRI`mNT¬
9
"
9
" ! #- ( 4 (0 . - '
9 pH
Indicator: THYMOL ÝLUE (' () ( *# - (4 (0 . !# - ' !#
2.2
- (-
; *-
2.4
- /(
; ,*
2.6
' -/
* ;'
2.8
' <*
* .(
9 Indicator: ÝROMOPHENOL ÝLUE (, -) . /# pH
- (4 (0 . !#
- ' !#
3.0
( -<
2 ;<
3.2
( .2
2 <,
3.4
( *<
2 '<
3.6
, ((
/ 2*
3.8
, <<
/ .<
4.0
, (<
/ '<
4.2
. '.
< */
4.4
. .'
< <;
4.6
. /2
< ,,
9 Indicator: CHLOROPHENOL RED (. *) / .# pH
- (4 (0 . !#
- ' !#
4.8
. ;,
< -2
5.0
< '<
. *<
5.2
< (-
. *-
5.4
< <*
. .(
5.6
< *-
. (-
5.8
/ -<
, ;<
6.0
/ ,'
, /;
6.2
/ /'
, ,;
6.4
/ ;(
, -*
9 Indicator: ÝROMOTHYMOL ÝLUE (/ -) 2 /# pH
- (4 (0 . !#
- ' !#
6.0
/ ,'
, /;
6.2
/ /'
, ,;
6.4
/ ;(
, -*
6.6
2 ,.
( //
6.8
2 2(
( (*
7.0
* (.
' 2/
7.2
* /;
' ,'
7.4
; -*
- ;(
7.6
; ,2
- /,
9 pH
Indicator: PHENOL RED (/ *) * -# - (4 (0 . !# - ' !#
6.8
2 2(
( (*
7.0
* (.
' 2/
7.2
* /;
' ,'
7.4
; -*
- ;(
7.6
; ,2
- /,
7.8
; <2
- .,
8.0
; 2(
- (*
<
$ $ $ $ $ $
- -'
"
< " 0 " "
& $ $ ( ($ ( .$( / ( *
6 $
6 $ "
" "- -'
'- ' 5'- '4 5*(
'- ' 5- '- '4 5* ;(
- '- ' 5'- '4 5* ;(
RmUT
Results ~
0.01M HOAc
4.8
Ý 1mL 0.1M HOAc + 1mL 0.1M NaOAc + 8mL H20 1mL 0.1M HOAc + 0.1mL 0.1M NaOAc + 8.9mL H2O 0.1mL 0.1M HOAc + 1mL 0.1M NaOAc + 8.9mL H2O
4.8 3.8 8.0
DICUION
Discussion
Preparation of Ýuffer Solutions
It is practical to use only the appropriate indicators for certain pH ranges because there will be no color transition in pH levels higher or lower than the respective range of the indicator.
If there is no color transition, the resulting indication of the pH of solutions will be very vague and there will be no firm basis for comparison.
Discussion
3=$ 4 & !84 9:8 9# $
Discussion
= " 84 9 8 9 & 84 9 8 9 &
~
0.01M HOAc
4.8
Ý 1mL 0.1M HOAc + 1mL 0.1M NaOAc + 8mL H20 1mL 0.1M HOAc + 0.1mL 0.1M NaOAc + 8.9mL H2O 0.1mL 0.1M HOAc + 1mL 0.1M NaOAc + 8.9mL H2O
4.8 3.8 8.0
a
,
5( , 5 5 ,
%
4 ,
4 5 5 ,
%
5( , 5 5 % 4 4 5 5 %
$ 4 ,
" ,
3 $ 4 ,
,
%
,
% ,
$ $ ,
5( , 5 5 4 ,
4 5 5
,
% ,
6 0
,
% " ,
, 5 $
$ $ $
îUIDmUmTION ¬ND¬NmR
' # " 6H of 0.01 M HOAc
4.8
[H3O+] of 0.01 M HOAc
j j
Yalculated Ka of HOAc
j
To get [H3O+]: pH = - log [H+] pH = - log [H3O+] [H3O+] = 10 -pH [H3O+] = 10 -4.8 [H3O+] = 1.58x10-5 M
6H of 0.01 M HOAc
4.8
[H3O+] of 0.01 M HOAc
1.58x10-5 M
Yalculated Ka of HOAc
j
" - -' " % ' <*&'-%< ; ;*&'-%,
5 5 % 5' <*&'-%< 5' <*&'-%< ' <*&'-%< ' <*&'-%<
78598 %9 7!' <*&'-%< #!' <*&'-%< #7( <-&'-%* 8 9 ; ;*&'-%,
( # & 4 ! $3 # " % !> (
'- ' 5'- '4 5*( '- ' 5- '- '4 5* ;( - '- ' 5'- '4 5* ;(
(
7%" 7% "!' *&'-%<#74.74 %
7 5"8 " 9 8 9
a
,
5( , 5 5 ,
%
4 ,
4 5 5 ,
% 5( , 5 5 % 4 4 5 5 %
5( , 5 5 % 4 4 5 5 % 6 " % 3 $
% 4 $ $ 8 %9784 9
Úorsolution¬: 1m1` O¬c 1m1`NaO¬cm O
@78 978 9 '1' 7( 1( !- '#!'#7!@#!'-# @7- -' 5( , 5 5 % 4 4 5 5 %
Úorsolution¬: 1m1` O¬c 1m1`NaO¬cm O
+78 " 9 78 %9784 9 '1' 7( 1( !- '#!'#7!+#!'-# +7- -' 5( , 5 5 % 4 4 5 5 %
Úorsolution¬: 1m1` O¬c 1m1`NaO¬cm O
7 5"8 " 9 8 9 7. 2.5"- -' - -' 7. 2.574.74 4.74
ÚorsolutionÝ: 1m1` O¬c 1m1`NaO¬c m O
@78 978 9 '1' 7( 1( !- '#!'#7!@#!'-# @7- -' 5( , 5 5 % 4 4 5 5 %
ÚorsolutionÝ: 1m1` O¬c 1m1`NaO¬c m O
+78 " 9 78 %9784 9 '1' 7( 1( !- '#!- '#7!+#!'-# +7- --' 5( , 5 5 % 4 4 5 5 %
ÚorsolutionÝ: 1m1` O¬c 1m1`NaO¬c m O
7 5"8 " 9 8 9 7. 2.5"- --' - -' 7. 2.% ' 73.74 3.74
ÚorsolutionC: 1m1` O¬c 1m1`NaO¬c m O
@78 978 9 '1' 7( 1( !- '#!- '#7!@#!'-# @7- --' 5( , 5 5 % 4 4 5 5 %
ÚorsolutionC: 1m1` O¬c 1m1`NaO¬c m O
+78 " 9 78 %9784 9 '1' 7( 1( !- '#!'#7!+#!'-# +7- -' 5( , 5 5 % 4 4 5 5 %
ÚorsolutionC: 1m1` O¬c 1m1`NaO¬c m O
7 5"8 " 9 8 9 7. 2.5"- -' - --' 7. 2.5' 75.74 5.74
Com6arison: ~olution
6H observed calculated
0.01 M HOAc
4.8
xxxxx
1 mL 0.1 M HOAc + 1 mL 0.1 M NaOAc + 8 mL H2O ï
4.8
4.74
1 mL 0.1 M HOAc + 0.1 mL NaOAc + 8.9 mL H2O ï
3.8
3.74
0.1 mL 0.1 M HOAc + 1 mL 0.1 M NaOAc + 8.9 mL H2O ï
8.0
5.74
CONCUION¬ND RmCO``mND¬TION
" $ & 3 $ " " "
3 " $ & $ " " &
,
$ , 5$ "
$ % $ "
$ " "
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