EXPERIMENT 1 : PREPARATION AND STANDARDISATION OF BASE AND ACID SOLUTION INTRODUCTION : Standardization is the ro!ess o" deter#inin$ the e%a!t !on!entration &#o'arit() o" a so'*tion+ Titration is one t(e o" ana'(ti!a' ro!ed*re o"ten *sed in standardization+ In a titration, an e%a!t -o'*#e o" one s*.stan!e is rea!ted /ith a 0no/n a#o*nt o" another s*.stan!e+ The oint at /hi!h the rea!tion is !o#'ete in a titration is re"erred re"erred to as the endoint+ A !he#i!a' s*.stan!e 0no/n as an indi!ator is *sed * sed to indi!ate &si$na') the endoint+ The indi!ator *sed in this e%eri#ent is heno'htha'ein+ Pheno'htha'ein, an or$ani! !o#o*nd, is !o'or'ess in a!idi! so'*tion and in0 in .asi! so'*tion+This e%eri#ent in-o'-es t/o searate a!id.ase standardization ro!ed*res+ In the "irst standardization the #o'arit( o" a sodi*# h (dro%ide so'*tion &NaO2) /i'' .e deter#ined .( titratin$ a sa#'e o" otassi*# a!id h tha'ate &32P4 23C526O6) /ith the NaO2+ In the se!ond ro!ed*re the standardized NaO2 /i'' .e *sed to deter#ine the #o'arit( o" a h(dro!h'ori! so'*tion &2C')+ OB7ECTI8E : To deter#ine deter#ine the !on!entration o" sodi*# h(dro%ide, h (dro%ide, h(dro!h'ori! a!id and the !on!entration ! on!entration o" *n0no/n a!id + MATERIALS : Sodi*# h(dro%ide, h(dro!h'ori! a!id , heno'htha'ein , .ea0er, -o'*#etri! "'as0, !oni!a' "'as0 , iette , .*rette, .*rette stand and !'a# , s#a'' "*nne' and iette "i'ter + PROCEDURE : i+
Standar Standardis disati ation on o" 9+1 M NaOh NaOh so'*ti so'*tion on /ith /ith 9+1 9+1 M otass otassi*# i*# h(dr h(dro$e o$en n htha' htha'ate ate++ 9 #' o" 32P /as iette into ;9 #' o" !oni!a' "'as0+ dros o" heno'htha'ein /as
dro as an indi!ator+ Potassi*# h(dro$en htha'ate /as titrate /ith 9+1 M Sodi*# h (dro%ide *nti' it t*rns 'i$ht in0+8o'*#e in0+8o'*#e o" Sodi*# h(dro%ide *sed /as re!orded + The titration /as reeat < ti#es+
ii+
Standardisation o" 9+1 M 2(dro!h'ori! a!id so'*tion /ith standardized Sodi*# h(dro%ide so'*tion + 9 #' o"sodi*# h(dro%ide /as iette into ;9 #' o" !oni!a' "'as0+ dros o"
heno'htha'ein /as dro as an indi!ator+ Then , it /as titrate /ith 9+1 M Sodi*# h(dro%ide *nti' it t*rns 'i$ht in0+8o'*#e o" Sodi*# h(dro%ide *sed /as re!orded + The titration /as reeat < ti#es+ iii+
Deter#ination o" the !on!entration o" *n0no/n h(dro!h'ori! a!id so'*tion+ 9 #' o" *n0no/n h(dro!h'ori! a!id so'*tion /as iette into ;9 #' o" !oni!a' "'as0+ dros o" heno'htha'ein /as dro as an indi!ator+ Then , it /as titrate /ith 9+1 M Sodi*# h(dro%ide *nti' it t*rns 'i$ht in0+8o'*#e o" Sodi*# h(dro%ide *sed /as re!orded + The titration /as reeat < ti#es+
RESULTS : Ta.'e 1+1 : Titration o" 0no/n #o'arit( o" 9+1 M sodi*# h(dro%ide + Tria' 1 9+1 +< + 9+9>91
Initia' .*rette readin$ NaO2 & #' ) Fina' .*rette readin$ NaO2 & #' ) 8o'*#e o" NaO2 *sed & #' ) Mo'arit(
Tria' 1+9 <+= += 9+955;
Ta.'e 1+ : titration o" *n0no/n #o'arit( o" 9+1 M h(dro!h'ori! a!id +
Initia' .*rette readin$ NaOh & #' ) Fina' .*rette readin$ NaOh & #' ) 8o'*#e o" NaOh *sed & #' ) Mo'arit(
Tria' 1 9+19 1>+>9 1>+>9 9+955>
Tria' 1>+>9 <>+>9 9+99 9+95><
Ta.'e < 1=+? <=+;9 1>+59 9+9556
Ta.'e 1+< : Titration o" *n0no/n #o'arit( o" h(dro!h'ori! a!id +
Initia' .*rette readin$ NaOh & #' ) Fina' .*rette readin$ NaOh & #' )
Tria' 1 +=9 ;9+59
Tria' >+>9 <1+;9
8o'*#e o" NaOh *sed & #' ) Mo'arit(
5+9 9+15=
<1+=9 9+1<==
CALCULATIONS : I+
Titration o" 0no/n #o'arit( o" 9+1 M NaOh ¿
Mo'arit(
volume KHP× molarity KHP volume NaOH
Tria' 1
Mo'arit(
¿
20 × 0.1 22.2
@ 9+9>91 M Tria' @ 9+955; M II+
Titration o" 0no/n #o'arit( o" 9+1 M 2(dro!h'ori! a!id ¿
Mo'arit(
Molarity of standardised NaOH ×Volume of standardised NaOH Volume of HCl
Tria' 1
Mo'arit(
¿
0.1 × 19.9 20
@ 9+955> M Tria' @ 9+95>< M
Tria' <
@9+9556 M III+
Titration o" *n0no/n #o'arit( o" h(dro!h'ori! a!id+ ¿
Mo'arit(
Molarity of standardised NaOH ×Volume of standardised NaOH Volume of HCl
Tria' 1
Mo'arit(
0.0893 × 28.2
¿
20
@ 9+1;> M Tria' @ 9+1611 M To $et # : Mo'arit(&M) % Ato#i! #ass&At t) @ $ra#s er 'iter&$') Ato#i! Mass &t+) o" 2C' @ <=+;95
9+1<<;#o'L%<=+;95 $#o' @6+5?<5 $' 6+5?<5 $' % 1999 @ 65?<+5 #$' @ 65?<+5 #
To $et
mg ml , 1 mg
4.8738 g
X
L
−3
4.8738 X 10
L μg To $et ml ,
−3
1 x 10
mg
@ 6+5?<5
1 L
%
−3
x 10
#$L
−6
x 10 1000 mL @ 6+5?<5
#$ #'
−6
4.8738 x 10
mg
mL
X
1 X 10
−3
g 1 μg @ 6+5?<5% 1 mg 1 mg
−3
10
μg / ml
DISCUSSIONS Sodi*# h(dro%ide is a se!ondar( standard+ A se!ondar( standard is a s*.stan!e /hi!h #a( .e *sed "or standardizations, and /hose !ontent o" the a!ti-e s*.stan!e has .een "o*nd .( !o#arison a$ainst a ri#ar( standard in this !ase is 32P+ It "o''o/s that, a se!ondar( standard so'*tion is a so'*tion in /hi!h the !on!entration o" disso'-ed so'*te has not .een deter#ined "ro# the /ei$ht o" the !o#o*nd disso'-ed .*t .( rea!tion o" a -o'*#e o" the so'*tion a$ainst a #eas*red -o'*#e o" a ri#ar( standard so'*tion + Based on the titration o" 0no/n #o'arit( o" sodi*# h(dro%ide a$ainst otassi*# h(dro$en htha'ate, the a-era$e !on!entration NaO2 is 9+95>< M+ The a!t*a' #o'arit( o" sodi*# h(dro%ide in this e%eri#ent is 9+1 M+D*e to the h($ros!oi! roert( o" se!ondar( standard, NaO2 readi'( a.sor.s #oist*re and rea!ts /ith the !ar.on dio%ide in the air+ For the se!ondar( titration , sodi*# h(dro%ide a$ainst the h(dro!h'ori! a!id +The a-era$e !on!entration o" NaO2 is 9+95> M+ This is to de ter#ine the !on!entration o" the 0no/n h(dro!h'ori! a!id +The a!t*a' !on!entration is 9+1 M +There is s'i$ht'( di""eren!e in the -a'*e o" the 2CL d*e to the sodi*# h(dro%ide *sed, /hi!h is a se!ondar( standard +The third titration, is to o.tain the !on!entration o" h(dro!h'ori! a!id /hi!h is 9+1<<; M +There is a'so s'i$ht'( di""eren!e /ith the a!t*a' /hi!h is 9+1; M +A$ain this is d*e to the NaO2 *sed +Besides that #is*d$e the !o'or o" the end oint a'so e""e!t the !on!entration+ This is .e!a*se hi$her -o'*#e o" NaO2 *sed+
A#on$ re!a*tion that #*st .e ra!ti!e is to .ein$ !are"*' to/ards the end o" the titration+ This is .e!a*se to a-oid o-er shoot -o'*#e o" titrant to/ards the a!id *sed+ Besides that , indi!ator are *sed to titrate a!id to o.ser-e the !o'or !han$e at the end oint+ The end oint o" a titration is indi!ated /hen the indi!ator !han$es !o'or+ An indi!ator is a /ea0 or$ani! a!id or .ase that has distin!t'( di""erent !o'ors in its nonionized and ionized "or#s+The indi!ator *sed is heno'htha'ein , /hi!h /i'' on'( rea!t /ith a!id+
CONCLUSION As !on!'*sion , the !on!entration o" sodi*# h(dro%ide is 9+95>< M, the 0no/n h(dro!h'ori! a!id is 9+95> M and the *n0no/n !on!entration o" h(dro!h'ori! a!id is 9+1<<; M +
REFERENCES 1+ htt:///+titrations+in"otitrationerrors + htts:///+dart#o*th+ed*!he#'a.te!hni*estitration+ht#' <+ htt:!he#+'i.rete%ts+or$CoreAna'(ti!a'Che#istr(La.Te!hni*esTitration
