Titration
: The quentities of the constituents
present in given unknown solution are determined by measuring the volumes of
solution taking part in a given chemical reaction. It is called titration.
(a)
Single Titration : When a solution of known conc. is used
to determine the conc. of an unknown solution.
(b)
Double titration : When 2 indication are used to determine
the composition of mixture of solution.
Basic
Terms used in Tiration
1)
Titre - It is a way of expressing concentration
it gives an approximate quantitate unformation from an analytical process.
2)
Titrant - Areagent called titrant when perpared in
volunetric analysis as otandard solution.
3)
Standard solution - A solution whose conecntration is known
to us is known as standard solution.
4) Unknown
solution - A solution whose concetration is not
known and is calcutated by the process of titration.
5)
Intermediate solution - A solution which
can react with standard and unknown solution and is used to find the
concentration of unknown solution.
6)
Indicator - A chemical substance which changes the
colour at the end point.
7) End
point - The stage during titration at which the
reaction is just complete i known as the end point of the titration.
8)
Equivalence point of stoichiometric point - The point at which the reaction between titre
and titrant is complete. This point does not show any change in colour.
Strendart
substance- In titration, standard substances are
clanified into foecousing two cakego ries on the basis of formation of
solution.
1)
Primary standard- A substance whose standard solution can
be prepared by mising appropriate amount of it in distilled water is known as
primary standared.
eg.
copper sulphate, ferrous ammonium sulphate, silver nitrate etc. It has
following characteristics:
i) It
is easily anaitable in state of high purity.
ii) It
is neither hydroscopic nor deliquescent.
iii) It
shown high solubility in water.
iv) It
does not dissociate or decompose during storage.
2)
Secondary standard - Substance whose stantard solutions cannot
be preapared directly it called secondary standard.
eg
Potassium permamgnate, Sodium hydroxide and Potossium hydroxide etc.
Working
of Double Titration -
a)
Titration between standard sollution and intermediate solution -
In this
experiment (step) we riuse pipette and conical flask with given standard
solution and pour standard solution in Burette. With the help of pipette, add
fixed amount of standard solution in conical flask. Add 3 to 4 drops of
suitable indicator in the flask. Allow solution placed in burette slowly,
dropwise in the flosk with continous stinning, till the equivalence point. is
attamed, non this reading of burette (as V2) unsing volume (V1) of standard solution, Normality of intermediate solution can
be determined.
b)
Titration between standard solution adn unknown solution- Using above procedure of titration of unknown solution with
standardised intermediate solution, vol (V3) of unknown solution and (V4) volume of intermediate solution can be determined. Following calculation
is used to find the concentration of unknown solution-
1. On
the basis of Normality-
a) To
Calculate concentration of unknown solution-
(Titration
between known solution and intermediate solution)
N1V1 = N2V2
N2 = .................(i)
When
N1 = Normality of known
solution
V1 = Volume of known
solution
N2 = Normality of
Intermediate solution
V2 = Volume of
Intermediate solution
b) (Titration between unknown solution and intermediate solution)
N3V3 = N4V4
N3 = 
.................(ii)
.................(ii)
When
N3 = Normality of unknown
solution
V3 = Volume of unknown
solution
N4 = Normality of
Intermediate solution
V4 = Volume of
Intermediate solution
using eq. (i) and (ii)
N3 =
c)
Concentration of unknown solution
=
equvalant weight
d)
percentage purity can be calculated using the formula-
% purity = 100
1. On the basis of Molarity-
We require a balanced chemical equation
eg aA+bBproducts
Where A
& B are reactance and a & b are mole numbers of A and B. Now, the
concertration i.e. molarity can be calculated as
MAVA = MBVB
Where
MA = Molarity of A
VA = Volume of A
MB = Molarity of B
VB = Volume of B
So, MB =
if a & b are in the ratio of 1:1,
then, formula can be written as
MAVA = MBVB
Types of Titration on the basis of
Reactions,
1) Acid
Base Titration - It is voluems the nutralisation reaction
between an acidic and a basic solution eg. Titration of NaOH with Ocalic acid.
2)
Redox Titration - It involues redox recation between the
analyte and titratant. It may involue the use of a redox indicator.
eg.
Titration of Mohr’s salt with Potassium Permanganate.
3)
Comploxometric Titration - It is a form of
volumetric analysis in which the formation of a colored complex is used to
indicate the end point of titration eg. Determination of degree of hardness of
water using EDTA.
4)
Precipitation Titration - It involues the
formation of insoluble precipitate which seare as a basis for a titration. eg.
Analysis of K2CO3 and K2SO4 in
potasle.
(1)
Acid Base Titration -
a)
Titration between strong Acid and strong base -
In such
cases, strong acid and strong base is used. At the equivalence point, equal
amoeuls of H+ and
OH- ions will combine to form H2O, resulting in a pH of 7.0 (Neutarl). eg. Strong acid H2SO4, HCl, HNO3 etc.
Strong
base - NaOH, KOH
b)
Titration between weak Acid and strong base -
It
involves the direct transfer of protons from the weak acid to hydroxide ion.
The reaction of weak acid with strong base like acetic acid and NaOH can be
seen below
C2H4O2 +OH- C2H3O2- + H2O
c)
Titration between strong Acid and weak base -
The pH
at the equvaleue point is not 7 but below it. This is because it forms a
conjugte acid during the titration and will react with water to produce H3O+ ions.
eg. NH4OH, Na2CO3 are weak bases and HCl,
H2SO4 are strong acids.
Methyl orange is used as an indicator when we take strong acid in burette.
Strong
base - NaOH, KOH
d)
Titration between weak Acid and weak base -
Weak
acids and weak base alnays exiset as conjugate acid base point in an equeous
solution pH does not change vigrously at end point.
Table 1.1
Table 1.2
Table 1.3
Equevalent
weight of acid=
Equevalent
weight of Base =
Preparation
of Starndard solution -
Generally
Acids and Bases exist in liquid or in solid form. While making dilute solution
of liquids acids or bases, Normaly is to be keep is mind. Following is the
table which gives the required amount of acids to be dissolued in 1 lit. to
prepare known strength of that solution.
Table 1.4
Table 1.5
AIM- Find the concentration of unknown Oxalic acid solution in gm
per litre given in bottle “B”. For this
purpose standard solution of crystalline
Oxalic acid is given in bottle “A” having molarity . Intermediate solution is
sodium Hydroxide and Phenolphthalin is used as an indicator.
Theory-It
is acidic-base titration. It is a double titration. With phenolphthalin
indicator it gives pink colour in base adn becomes colourless in acidic medium.
Chemical Reaction -
H2C2O4 + 2
NaOH Na2C2O4 +
2H2O
Ionic Reaction -
H+ +
OH- H2O
Apparaturs and Matericals required -
Burette,
pipette, conical flask, funnel, burette stand, NaOH solution, Oxalic acid solution, indicator Phenolphthalin ,
distiled water etc.
Method-
a)
Titration of std. Oxalic acid solution with NaOH solution
Fill
burette with NaOH intermidiate solution and Pipette out 20 ml known Oxalic acid
solution in conical flosk add 2-3 drops of phenolphthalin indicator. Do the
titration as discussed in Ex. No. 01 and find the Concordant Reading.
b)
Titration of Unknown Oxalic acid solution with intermediate NaOH solution
Fill
burette with intermediate NaOH solution and pipette out 20 ml of unknown oxalic
acid. Add 2-3 drops of phenolphthalin indicator. Repeat the process of
titration and find the concordant reading.
Obseration Table 1
a) Titration between known Oxalic acid and
intermediate solution.
Sr. No.
|
Vol. of Known Oxalic acid solution
|
Burette Reading
|
Vol. of NaOH Solution
|
Concordant
Volume
|
|
Initial
|
Final
|
||||
1
|
20 ml.
|
0.0
|
|||
2
|
20 ml
|
0.0
|
|||
3
|
20 ml
|
0.0
|
|||
Obseration Table 2
a) Titration between unknown Oxalic acid
and intermediate solution.
Sr. No.
|
Vol. of Unnown Oxalic acid solution
|
Burette Reading
|
Vol. of NaOH Solution
|
Concordant
Volume
|
|
Initial
|
Final
|
||||
1
|
20 ml.
|
0.0
|
|||
2
|
20 ml
|
0.0
|
|||
3
|
20 ml
|
0.0
|
|||
Calculation
-
a)
Molarity of Given Oxalic acid solution = M/30
b) a1M1V1 = a2M2V2
a1 = 2
a2 = 1
M1 = M/30 Molarity of std.
Oxalic acid solution.
M2 = Molarity of
Intermediate NaOH solution.
V1 = Volume of std. Oxalic
acid solution.
V2 = Volume of Intermediate
NaOH solution.
M2 = =2M
c)
Molarity of unknown Oxalic acid solution.
2M3V3 = M4V4
M3 = Molarity of unknown
Oxalic acid solution=
?
M4 = Molarity of
Intermediate NaOH solution. =2M
V3 = Volume of unknown
Oxalic acid solution.=
20 ml
V4 = Volume of Intermediate
NaOHsolution. =
M3 = =M
=M
d)
Concentration of unknown oxalic acid
Concentratin
= molarity x mol. mass of crystalline oxalic acid
=
M126 = 6.1456 gm/lit.
AIM- Find out the molarity of unknown sloution of sodium carbonate
given in bottle ‘B’. For this purpose standard
solution of crystaline Sodium carbonate is given in Bottle ‘A’ having molarity
M/20. intermediate solution is HCl. indicator : Methyl orange
Theory-a)
this is neutralisation titration.
b)
This is double titration.
c)
Methyl orange gives orange colour in basic and pink colour in acidic medium.
Chemical Reaction -
Na2CO3 + 2HCl 2NaCl + H2O + CO2
Apparaturs and Matericals required -
Burette,
pipette, conical flask, funnel, burette stand, Na2CO3 solution, HCl solution, indicator methyl
orange, distiled water etc.
Method-
a)
Titration of std. Na2CO3 solution with HCl
solution
Wash
Burette with water followed by washing with HCl solution. Then fill burette
with HCl solution by placing it in stand.
New
pitpette out 20 ml of Std. solution in conical flask. Add 2-3 drops of
indicator in the flask. Allow the solution of burette to add in the flask drop
by drop with continous stinning.
At
the equvatence point, pink colour appears. Note the burette reading to
calculate the molority of solution repeat the process to get concordant
reading.
b)
Titration of Unknown solution with intermediate solution
Take
intermediate solution in burette, and pipette out 20 ml in conical flask. Add
2-3 drops of indicator.
Now
add solution from burette in the flask drop by drop, fill pink colour comes at
end point.
Obseration Table 1
Obseration Table 2
Calculation
-
a)
Molarity of Given Na2CO3 = M/20
b) a1M1V1 = a2M2V2
a1 = 2
a2 = 1
M1 = M/20 Molarity of std.
Na2CO3 solution.
M2 = Molarity of
Intermediate HCl solution.
V1 = Volume of std. Na2CO3 solution.
V2 = Volume of Intermediate
HCl solution.
M2 = =2M
c)
Molarity of unknown Sodium Carbonate solution.
2M3V3 = M4V4
M3 = Molarity of unknown Na2CO3 solution.= ?
M4 = Molarity of
Intermediate HCl solution. =2M
V3 = Volume of unknown Na2CO3 solution.= 20 ml
V4 = Volume of Intermediate
HCl solution. =
M3 = =M
=M
Result- Molarity of unknown sodium carbonate is
................... mol/Lit.
AIM- To find the % purity of unknown ferrous ammonium sulphate given
in bottle B. Its sample is prepared by mixing 14.0 gm in 1 lit. of solution.
For this, you are provided with std. solution of ferrous ammonium sulphate fo
13.0666 g/l. concentration given in bottle A. intermediate solution is KMnO4
Theory-It
is a redox reaction where ferrous ammonium sulphate also acts as reducing agent
just-like oxalic acid.
Chemical
reacting takes place
oxn half reaction
FeSO4(NH4)2SO4.6H2O + H2SO4 +[O]Fe2(SO4)3 + (NH4)2 SO4 + 7H2O
Redn half reaction
KMnO4+3H2SO4K2(SO4) + Mn SO4 + 3H2O +5[O]
Apparaturs
and Matericals required -
Burette,
pipette, conical flask, funnel, burette stand, washing bottle, Ferrous ammonium
sulphate solution, (Known & unknown), KMnO4 solution, distilled
water, dil H2SO4 .
Procedure
-
a)
Titration of Intermeidate KMnO4 solution with known
Ferrous ammonium sulphate
Fill
the burette with intermediate KMnO4 after riusing with wath.
Now take 20 ml of known ferrous ammonium sulphate solution in a conical flask,
and then add around 10 ml of dil H2SO4. Now add KMnO4 dropwise in the conical
flask till permanent pink colour appears, this is the end point, repeat the
process to get concordant reading.
b)
Titration of Unknown Ferrous ammonium sulphate solution with intermediate KMnO4 solution
Fill
burette with intermediate solution, and fill conical flask with ferrous
ammonium sulphate solution wsing pipette. Now add 10 ml of dil. H2SO4and find the end point repeat the process
to get concordant reading.
Obseration Table 1
a) Titration between intermediate KMnO4 solution with known solution FAS solution.
Obseration Table 2
b) Titration between unknown solution and
intermediate KMnO4 solution.
Calculation
-
a)
Molarity of std. Ferrous ammonium sulphate solution
Molarity =
=M
b)
Molarity of intermediate KMnO4 solution
M1V1 =
5M2V2
where,
M1 = Molarity of known
Ferrous ammonium sulphate solution.=M
M2 = Molarity of intermediate
KMnO4 solution.= ?
V1 = Volume of known FAS
solution.= 20 ml
V2 = Volume of intermediate
KMnO4 solution.= x ml
c)
Molarity of unknown FAS solution.
M3V3 =
5M4V4
M3 = Molarity of known FAS solution.
M4 = Molarity of intermediate
KMnO4 solution. =M
V3 = Volume of known FAS
solution. = 20 ml
V4 = Volume of intermediate
KMnO4 solution. = y ml
d)
strength of unknown oxalic acid
strength =
molarity x mol. mass of crystalline oxalic acid
=
392.12 = ......... gm/lit.
e) %
purity of unknown FAS
=100
=100 = ............%
Result :
Perecent purity of unknown crystalline FAS solution is ............%.
You may
use normality in place molarity.
a)
Normality of standred oxalic acid
Normality
=
N1 =N
b)
Normality of intermediate KMnO4 solution.
N1V1 = N2V2
N1 = Normality of std.FAS
solution.=N
N2 = Molarity of
Intermediate KMnO4 solution. = ?
V1 = Volume of std. FAS solution.
= 20 ml
V2 = Volume of Intermediate
KMnO4 solution. = x ml
N2 = =N
c)
Normality of unknown FAS solution.
N3V3 = N4V4
N3 = Normality of unknown
FAS solution.= ?
N4 = Normality of
Intermediate KMnO4 solution.
=N
V3 = Volume of unknown FAS
solution.= 20 ml
V4 = Volume of
Intermediate KMnO4 solution. =y ml
N3 = =N
=N
d)
Strength of unknown FAS
Strength =
Normality Eq. wt. of FAS
=392.12
=
...... gm/lit
e) %
Purity of unknown FAS
% purtiy =
100 = 100 = ............%
Result- % purity of unknown crystalline FAS is ............%
Potassium
dichromate titration
a)
Normality of std. sodium carbonate
Normality
=
=
g/l
b)
Normality of std. Hydrochloric acid solution
N1V1 = N2V2
N1 = Normality of
std.oxalic acid solution.= N
N2 = Molarity of
Intermediate HCl solution. = ?
V1 = Volume of std. Oxalic
acid solution.
= 20 ml
V2 = Volume of Intermediate
HCl solution. = x ml
N2 = =N
c)
Normality of unknown Sodium Carbonate solution.
N3V3 = N4V4
N3 = Normality of unknown
Na2CO3 solution.= ?
N4 = Normality of
Intermediate HCl solution. = y N
V3 = Volume of unknown Na2CO3 solution.= 20 ml
V4 = Volume of Intermediate
HCl solution. =y ml
N3 = =N
=N
Result- Normality of unknown sodium carbonate is N.
Exp. 1
AIM- Calculate the molarity of unknown sodium carbonate given in
bottle B. You are provided with M/20 standard solution of Sodium carbonate solutin
in Bottle A. By Titration method using methyl orange as an indicator and
intermediate solution is HCl.
Theory-a)
this is neutralisation titration.
b)
This is double titration.
c)
Methyl orange gives orange colour in basic and pink colour in acidic medium.
Chemical Reaction -
Na2CO3 + 2HCl 2NaCl + H2O + CO2
Apparaturs and Matericals required -
Burette,
pipette, conical flask, funnel, burette stand, Na2CO3 solution, HCl solution, indicator methyl
orange, distiled water etc.
Method-
a)
Titration of std. Na2CO3 solution with HCl
solution
Wash
Burette with water followed by washing with HCl solution. Then fill burette
with HCl solution by placing it in stand.
New
pitpette out 20 ml of Std. solution in conical flask. Add 2-3 drops of indicator
in the flask. Allow the solution of burette to add in the flask drop by drop
with continous stinning.
At
the equvatence point, pink colour appears. Note the burette reading to
calculate the molority of solution repeat the process to get concordant reading.
b)
Titration of Unknown solution with intermediate solution
Take
intermediate solution in burette, and pipette out 20 ml in conical flask. Add
2-3 drops of indicator.
Now
add solution from burette in the flask drop by drop, fill pink colour comes at
end point.
Obseration Table 1
Obseration Table 2
Calculation
-
a)
Molarity of Given Na2CO3 = M/20
b) a1M1V1 = a2M2V2
a1 = 2
a2 = 1
M1 = M/20 Molarity of std.
Na2CO3 solution.
M2 = Molarity of
Intermediate HCl solution.
V1 = Volume of std. Na2CO3 solution.
V2 = Volume of Intermediate
HCl solution.
M2 = =2M
c)
Molarity of unknown Sodium Carbonate solution.
2M3V3 = M4V4
M3 = Molarity of unknown Na2CO3 solution.= ?
M4 = Molarity of
Intermediate HCl solution. =2M
V3 = Volume of unknown Na2CO3 solution.= 20 ml
V4 = Volume of Intermediate
HCl solution. =
M3 = =M
=M
Result- Molarity of unknown sodium carbonate is
................... mol/Lit.
Exp. 2
AIM- Find the concentration in gm per litre of unknown Oxalic acid
solution given in bottle B. You are provided with standard crystalline Oxalic
acid solution whose 12.68 gm of oxalic acid is disolved in 1 lit in bottle
A. Intermediate solution is sodium
Hydroxide and Phenolphthalin is used as an indicator.
Theory-It
is acidic-base titration. It is a double titration. With phenolphthalin
indicator it gives pink colour in base adn becomes colourless in acidic medium.
Chemical Reaction -
H2C2O4 + 2
NaOH Na2C2O4 +
2H2O
Apparaturs and Matericals required -
Burette,
pipette, conical flask, funnel, burette stand, NaOH solution, Oxalic acid solution, indicator Phenolphthalin ,
distiled water etc.
Method-
a)
Titration of std. Oxalic acid solution with NaOH solution
Fill
burette with NaOH intermidiate solution and Pipette out 20 ml known Oxalic acid
solution in conical flosk add 2-3 drops of phenolphthalin indicator. Do the
titration as discussed in Ex. No. 01 and find the Concordant Reading.
b)
Titration of Unknown Oxalic acid solution with intermediate NaOH solution
Fill
burette with intermediate NaOH solution and pipette out 20 ml of unknown oxalic
acid. Add 2-3 drops of phenolphthalin indicator. Repeat the process of
titration and find the concordant reading.
Obseration Table 1
a) Titration between known Oxalic acid and
intermediate solution.
Obseration Table 2
a) Titration between unknown Oxalic acid
and intermediate solution.
Calculation
-
a)
Normality of std. sodium carbonate
Normality
=
=
g/l
b)
Normality of std. Hydrochloric acid solution
N1V1 = N2V2
N1 = Normality of
std.oxalic acid solution.= N
N2 = Molarity of
Intermediate HCl solution. = ?
V1 = Volume of std. Oxalic
acid solution.
= 20 ml
V2 = Volume of Intermediate
HCl solution. = x ml
N2 = =N
c)
Normality of unknown Sodium Carbonate solution.
N3V3 = N4V4
N3 = Normality of unknown
Na2CO3 solution.= ?
N4 = Normality of
Intermediate HCl solution. = y N
V3 = Volume of unknown Na2CO3 solution.= 20 ml
V4 = Volume of Intermediate
HCl solution. =y ml
N3 = =N
=N
Result- Normality of unknown sodium carbonate is N.
Oxidation-
Reduction (Redox) titrations.
Redox reactions -It is a type of titration based on a redox
reaction (which involves the reaction two species where one reaceant undergo
reduction while other undergo oxidation reaction between analyte adn titreat.
It may
involves the use of redox indicator and / or a potentiometer.
Preparation
of solution - On such titration one substance acts as reducing agent. To
prepare std. solution we should how hnowledge of equivalent weight.
To calculate
eq. wt. of oxidant and reducataut.
Eq. wt. of
oxidising agent =
or
Equivalent wt. =
eg. eq.
wt. of KMnO4 =
In acidic
medium
MnO4- + 8H+ + e- Mn2+ + 4H2O
Mol. mass
of KMnO4 =158
No of e- gained = 5
So, Eq. wt. = = 31.6
In basic
medium
MnO4- + 3 e- + 2H2OMnO2 +
4OH-
So, No of e- gained = 3
So, Eq. wt. = = 52.66
In neutral
medium
MnO4- + 2H2O + 3 e- MnO2 + 4OH-
So, Eq. wt. = = 52.66
2. Eq. wt of K2Cr2O7
Cr2O72- +
14H+ + 6
e- 2Cr3+ + 7H2O
Mol. mass
of K2Cr2O7 =294
No of e- gained = 6
So, Eq. wt. = = 49
3. Eq. wt
of ferrous sulphate
Fe2+ Fe3+ + e-
Mol. mass
of FeSO4.7H2O =278
No of e- lost per moleculer = 1
So, Eq. wt. = = 278
4. Eq. wt
of Mohr’s slat [FeSO4.(NH4)2SO4.6H2O]
Fe2+ Fe3+ + e-
Mol. mass
of Mohr’s salt =392
No of e- lost per moleculer = 1
So, Eq. wt. = = 392
5. Eq. wt
of Oxalic acid (H2C2O4.2H2O)
(C2O4)-2 2CO2 + 2e-
Mol. mass
of Oxalic acid =126
No of e- lost per moleculer = 2
So, Eq. wt. = = 63
Now eq.
wt. of acid can be
Calcuted
as =
== 63
So, Eq.
wt. of oxalic acid = 63
Table 1.6 shows amount of different substances taken for
different conc. of solution.
Exp. 4
AIM- Find the concentration in (gm per litre) of unknown Oxalic acid
solution given in bottle B. Using the std. solution of crystiline of oxalic
acid for which 4.2026 g/l in Bottle A.
Intermediate solution is Potasium permanganate.
Theory-We
all know that KMnO4 acts as strong oxidising agent in acidic medium can be
shows by following reaction.
MnO4- + 8H+ + 5 e- Mn+2 + 4H2O
In
this titration, dil. H2SO4 acid to make the medium
acid. We cannot used Nitric acid because HNO3 is itself an oxidising
agent. HCl can not be used because it reacts with KMnO4 as shown below
2KMnO4 + 16HCl2KCl + 5Cl2 + 8H2O + 2MnCl2
oxalic
acid in this reaction acts as acducing agent .
following
reacting takes place
reactions
of oxalic acid
2KMnO4 + 3H2SO4K2SO4+ 2MnSO4 + 3H2O + 5[O]
{H2C2O4 + [O] 2CO2+H2O} 5
net
reaction
2KMnO4 + 3H2SO4 +
5 H2C2O4 K2SO4 +
2MnSO4 + 8H2O + 10CO2
Ionic equation
[MnO4- + 5 e- + 8H+Mn+2 +
4H2O]2
[C2O4-2 +
2CO2 + 2
e-]5
net
reaction
2MnO4- +5C2O4-2 + 16H+2Mn+2 +
10CO2+8H2O
In
these reactions MnO4- ion
gets reduced to Mn+2, and C2O4-2 ions gets oxidised to CO2 . So that C cahnges its
oxn No.
from +3 to +4, where KMnO4 acts as self indicator. Initially when the
reaction between oxalic acid and KMnO4 takes place and thus
colour of KMnO4 disappears but at end point where oxalic acid
is completely conseumed, KMnO4 shows its colour. In adding to the doing the
reaction mix. of oxalic acid KMnO4 & dil. H2SO4 in
heated at about 500C, became this reaction. takes place at
high temperature. In this reaction, KMnO4 changes to MnSO4 which acts as catalyst
with aley ratc of reaction is slow but as the reaction proeceds, rate of
reaction.
Apparaturs and Matericals required -
Burette,
pipette, conical flask, funnel, burette stand, washing bottle, Oxalic acid
solution, (Known & unknown), KMnO4 solution, distilled
water, dil H2SO4 .
Procedure
-
a)
Titration of Intermeidate KMnO4 solution with known
oxalic acid
Wash
the bottle first with distilled water and then with intermediated KMnO4 solution at 0 reading.
Now take 20 ml in conical flask and heat at 500C tempereture, add aroound 10 ml of dil. H2SO4 to
take the medium acidic. add KMnO4 drop from the burette in the flask and find
the end point where pink colour of KMnO4 reaction. Repeat the
procers till concordant readings are obtained.
b)
Titration of Unknown Oxalic acid solution with intermediate KMnO4 solution
Now
fill the burette with intermediate KMnO4 after rising with
distilled water. Take unknown oxlac acid in conical flask using pipette (20
ml). Now heat the flask to 500C, and
then add arount 10 ml of dil. H2SO4. Do the process of titration and find the concordant reading.
Obseration Table 1
a) Titration between intermediate solution
with known solution.
Obseration Table 2
b) Titration between unknown Oxalic acid
and intermediate solution.
Calculation
-
a)
Molarity of std. oxalic acid solution
Molarity =
=M
b)
Molarity of intermediate KMnO4 solution
n1M1V1 = n2M2V2
2M1V1 =
5M2V2
where,
M1 = Molarity of known
oxalic acid solution.
M2 = Molarity of intermediate
KMnO4 solution.
V1 = Volume of known oxalic
acid solution.
V2 = Volume of intermediate
KMnO4 solution.
M2 = =M
c)
Molarity of unknown oxalic acid solution.
2M3V3 =
5M4V4
M3 = Molarity of known
oxalic acid solution.
M4 = Molarity of intermediate
KMnO4 solution. =M
V3 = Volume of known oxalic
acid solution. = 20 ml
V4 = Volume of intermediate
KMnO4 solution. = y ml
M3 =
d)
strength of unknown oxalic acid
strength =
molarity x mol. mass of crystalline oxalic acid
=
126= ......... gm/lit.
Result :
Strength of unknown crystalline oxalic acid solution is ............gm/lit.
You may
use normality in place molarity.
a)
Normality of standred oxalic acid
Normality
=
N1 =N
b)
Normality of intermediate KMnO4 solution.
N1V1 = N2V2
N1 = Normality of
std.oxalic acid solution.=N
N2 = Molarity of
Intermediate KMnO4 solution. = ?
V1 = Volume of std. Oxalic
acid solution.
= 20 ml
V2 = Volume of Intermediate
KMnO4 solution. = x ml
N2 = =N
c)
Normality of unknown oxalic acid solution.
N3V3 = N4V4
N3 = Normality of unknown
oxlaic acid solution.= ?
N4 = Normality of
Intermediate KMnO4 solution.
=N
V3 = Volume of unknown
oxalic acid solution.= 20 ml
V4 = Volume of Intermediate KMnO4 solution. =y ml
N3 = =N
=N
d)
Strength of unknown oxalic acid
Strength =
Normality Eq. wt. of oxalic acid
=
63.04
=
...... gm/lit
Result- Strength
of unknown crystalline oxalic acid is gm/lit.
Exp. 5
AIM- To find the % purity of unknown ferrous ammonium sulphate given
in bottle B. Its sample is prepared by mixing 14.0 gm in 1 lit. of solution.
For this, you are provided with std. solution of ferrous ammonium sulphate fo
13.0706 g/l. concentration given in bottle A. intermediate solution is KMnO4
Theory-It
is a redox reaction where ferrous ammonium sulphate also acts as reducing agent
just-like oxalic acid.
Chemical
reacting takes place
oxn half reaction
FeSO4(NH4)2SO4.6H2O + H2SO4 +[O]Fe2(SO4)3 + (NH4)2 SO4 + 7H2O
Redn half reaction
KMnO4+3H2SO4K2(SO4) + Mn SO4 + 3H2O +5[O]
Apparaturs
and Matericals required -
Burette,
pipette, conical flask, funnel, burette stand, washing bottle, Ferrous ammonium
sulphate solution, (Known & unknown), KMnO4 solution, distilled water,
dil H2SO4 .
Procedure
-
a)
Titration of Intermeidate KMnO4 solution with known
Ferrous ammonium sulphate
Fill
the burette with intermediate KMnO4 after riusing with wath.
Now take 20 ml of known ferrous ammonium sulphate solution in a conical flask,
and then add around 10 ml of dil H2SO4. Now add KMnO4 dropwise in the conical
flask till permanent pink colour appears, this is the end point, repeat the
process to get concordant reading.
b)
Titration of Unknown Ferrous ammonium sulphate solution with intermediate KMnO4 solution
Fill
burette with intermediate solution, and fill conical flask with ferrous
ammonium sulphate solution wsing pipette. Now add 10 ml of dil. H2SO4and find the end point repeat the process
to get concordant reading.
Obseration Table 1
a) Titration between intermediate KMnO4 solution with known solution FAS solution.
Obseration Table 2
b) Titration between unknown solution and
intermediate KMnO4 solution.
Calculation
-
a)
Molarity of std. Ferrous ammonium sulphate solution
Molarity =
=M
b)
Molarity of intermediate KMnO4 solution
M1V1 =
5M2V2
where,
M1 = Molarity of known
Ferrous ammonium sulphate solution.=M
M2 = Molarity of intermediate
KMnO4 solution.= ?
V1 = Volume of known FAS
solution.= 20 ml
V2 = Volume of intermediate
KMnO4 solution.= x ml
c)
Molarity of unknown FAS solution.
M3V3 =
5M4V4
M3 = Molarity of known FAS solution.
M4 = Molarity of intermediate
KMnO4 solution. =M
V3 = Volume of known FAS
solution. = 20 ml
V4 = Volume of intermediate
KMnO4 solution. = y ml
d)
strength of unknown oxalic acid
strength =
molarity x mol. mass of crystalline oxalic acid
=
392.12 = ......... gm/lit.
e) %
purity of unknown FAS
=100
=100 = ............%
Result :
Perecent purity of unknown crystalline FAS solution is ............%.
You may
use normality in place molarity.
a)
Normality of standred oxalic acid
Normality
=
N1 =N
b)
Normality of intermediate KMnO4 solution.
N1V1 = N2V2
N1 = Normality of std.FAS
solution.=N
N2 = Molarity of
Intermediate KMnO4 solution. = ?
V1 = Volume of std. FAS solution.
= 20 ml
V2 = Volume of Intermediate
KMnO4 solution. = x ml
N2 = =N
c)
Normality of unknown FAS solution.
N3V3 = N4V4
N3 = Normality of unknown
FAS solution.= ?
N4 = Normality of
Intermediate KMnO4 solution.
=N
V3 = Volume of unknown FAS
solution.= 20 ml
V4 = Volume of
Intermediate KMnO4 solution. =y ml
N3 = =N
=N
d)
Strength of unknown FAS
Strength =
Normality Eq. wt. of FAS
=392.12
=
...... gm/lit
e) %
Purity of unknown FAS
% purtiy =
100 = 100 = ............%
Result- % purity of unknown crystalline FAS is ............%
Potassium
dichromate titration
Introdution
- Reaction between K2Cr2O7 and
Ferrous ion is a redox reaction, when Fe+2 salt acts as reducing
agent and acidic K2Cr2O7 act
as an oxidising.
Following
is the reaction takes place :-
Cr2O7-2 +
Fe+2 +
14 H+ 2Cr+3 + 6 Fe+3 + 7 H2O
In this
reaction, Fe+2 is oxidised to Fe+3 . For the determination
of Fe+2, K2Cr2O7 is more suitable then
KMnO4 this is because:-
a) Std.
solution of K2Cr2O7 can be prepared.
b) Its aq
solution does not dissociate on standing for longer time.
c) To make
the medium acidic dil. HCl can also be used in addtion be dil. H2SO4.
d) K2Cr2O7 can not be reduced by the carbonic impurities proseut in H2O.
N-Phenyl
Anthranlic acid is used as an internal indicator for this reaction.
K4[Fe(CN)6] can be used as an external indicator.
N-Phenyl
anthranillic acid - This is green in colour. When it reacts with K2Cr2O7 green color changes to
porple colour. In the titration between Ferrous salt and K2Cr2O7 , Ferrous ion gets oxidised to Ferric ions.
Following
is the structure of N-Phenyl Anthranillic acid which changes from green to
purple colour.
+ +H2O
Green
Coloour
Violet
Colour
Preparation
of N-Phenyl anthrallic acid - Mix 1 gm
N-Phenyl anthrallic acid in 15 ml solution of 0.1 N NaOH and to make it
up to 1 litre by adding distilled water. use 5-6 drops of this indicator every
time. You can use diphynyl amine also in case
N-Phenyl anthrallic acid.
Exp. 6
AIM- To calculate the conc. of Ferrous Ammonium sulphate in gm/lit.
in bottle B. N/30 Ferrous ammonium sulphate is given bootle A. K2Cr2O7 is used as intermidiate
solution, indicator given is N-Phenyl anthrallic acid.
Theory-K2Cr2O7 in acidic medium,
oxadises Fe+2 to
Fe+3 ions. colour of indicator changes from green
to perple as per the following chemical reaction.
K2Cr2O7+FeSO4(NH4)2SO4.6H2O + 7 H2SO4 K2SO4 +Cr2(SO4)3 +3Fe2(SO4)3 + 6(NH4)2 SO4 + 48H2O
Ionic reaction
Cr2O7-2 + 6 Fe+2+ 14H+Cr+3 + 6 Fe+3+ 7H2O
Procedure
-
Fill
K2Cr2O7 sollution in the burette and pipette out 20 ml
fo FAS in conical flask and add around 10 ml dil H2SO4 .and 4-5 drops of indicator, at the end point
green colour. Repeat the process to get concordant reading.
Obseration Table 1
a) Titration of std FAS with intermediate
K2Cr2O7 solution
Obseration Table 2
b) Titration between unknown FAS solution
and intermediate K2Cr2O4 solution.
Calculation
- Titration of Std. FAS with Std. K2Cr2O7
FAS = K2Cr2O7
N1V1 = N2V2
N1 = Normality of std.FAS
solution.
N2 = Normality of
Intermediate solution. = ?
V1 = Volume of std. FAS solution.
= 20 ml
V2 = Volume of Intermediate
solution. = x ml
20 = N2 x ml
N2 =
b)
Titration of intermediate solution with unknown FAS
FAS = K2Cr2O7
N3V3 = N4V4
N3 = Normality of unknown
FAS solution.= ?
N4 = Normality of
Intermediate K2Cr2O7 solution.
V3 = Volume of unknown FAS
solution.= 20 ml
V4 = Volume of
Intermediate K2Cr2O7 solution. =y ml
N3 20 = N4 y ml
N3 20 = y ml
N3 = 392.12
Result- Strength unknown crystalline FAS is ...........gm/liter.
Exp. 7
AIM- To find the strength (in g/l) for given Ferrous Ammonium
sulphate in bottle B. Bottle A contains
12.2536 gm/liter standred solution of FAS. Intermidiate solution is K2Cr2O7 .
Indicator N-Phenyl anthrallic acid.
Theory-
Reaction between K2Cr2O7 and
FAS is a redox reactin, where Fe+2 gets oxidixed to Fe+2 to Fe+3 ions. and Cr+6 is reduced to Cr+3.
Chemical
reaction
K2Cr2O7+7FeSO4(NH4)2SO4.6H2O + 7 H2SO4 K2SO4 +Cr2(SO4)3 +3Fe2(SO4)3 + 6(NH4)2 SO4 + 43H2O
Ionic reaction
Cr2O7-2 + 6
Fe+2+ 14H+Cr+3 + 6
Fe+3+ 7H2O
Obseration Table 1
a) Titration of std FAS with intermediate
K2Cr2O7 solution
Obseration Table 2
b) Titration between unknown FAS solution
and intermediate K2Cr2O4 solution.
Calculation
-
i)
Normality fo std. FAs solution
N = =
ii)
Titration between std FAS and intermediat K2Cr2O7
FAS = K2Cr2O7
N1V1 = N2V2
N1 = Normality of std.FAS
solution.
N2 = Normality of
Intermediate solution. = ?
V1 = Volume of std. FAS solution.
= 20 ml
V2 = Volume of Intermediate
solution. = x ml
N 20 = N2 x ml
iii)
Titration between unknown FAS and intermediat K2Cr2O7
b)
Titration of intermediate solution with unknown FAS
N3V3 = N4V4
FAS = K2Cr2O7
N3 = Normality of unknown
FAS solution.= ?
N4 = Normality of
Intermediate K2Cr2O7 solution.
V3 = Volume of unknown FAS
solution.= 20 ml
V4 = Volume of
Intermediate K2Cr2O7 solution. =y ml
N3 20 = N4 y ml
N3 20 = y ml
N3 =
iv)
Concentration of unknown FAS
Concentration
= Normality Eq. wt.
Strength =
278
=
............ g/lit.
Result- Strength unknown crystalline FAS given in bottle B is ...........gm/liter.
Exp. 8
AIM- To find the percentage purity of crystllin Ferrous Ammonium
sulphate given in bottle B. Which is
properad by mixing 12.0 gm per litre of impure sample. You are provided with
6.5352 gm per 500 ml of known FAS in Bottle A.
Intermidiate solution is K2Cr2O7 and Indicator is N-Phenyl anthrallic acid.
Theory-
Reaction between K2Cr2O7 and
FAS is a redox reactin, where Fe+2 gets oxidixed to Fe+2 to Fe+3 ions. and Cr+6 is reduced to Cr+3.
Chemical
reaction
K2Cr2O7+7FeSO4(NH4)2SO4.6H2O + 7 H2SO4 K2SO4 +Cr2(SO4)3 +3Fe2(SO4)3 + 6(NH4)2 SO4 + 43H2O
Ionic reaction
Cr2O7-2 + 6
Fe+2+ 14H+Cr+3 + 6
Fe+3+ 7H2O
Obseration Table 1
a) Titration of std FAS with intermediate
K2Cr2O7 solution
Obseration Table 2
b) Titration between unknown FAS solution
and intermediate K2Cr2O4 solution.
Calculation
-
i)
Normality fo std. FAs solution
N = =
ii)
Titration between std FAS and intermediat K2Cr2O7
FAS = K2Cr2O7
N1V1 = N2V2
N1 = Normality of std.FAS
solution.
N2 = Normality of
Intermediate solution. = ?
V1 = Volume of std. FAS solution.
= 20 ml
V2 = Volume of Intermediate
solution. = x ml
N 20 = N2 x ml
N2 =N
iii)
Titration between unknown FAS and intermediat K2Cr2O7
b)
Titration of intermediate solution with unknown FAS
N3V3 = N4V4
FAS = K2Cr2O7
N3 = Normality of unknown
FAS solution.= ?
N4 = Normality of
Intermediate K2Cr2O7 solution.
V3 = Volume of unknown FAS
solution.= 20 ml
V4 = Volume of
Intermediate K2Cr2O7 solution. =y ml
N3 20 = N4 y ml
N3 20 = y ml
N3 = N
iv)
Concentration of unknown FAS
Concentration
= Normality Eq. wt.
Strength =
278
=
............ g/lit.
v)
Percentage purity of unknown FAS
= 100.
=
100
=
............ %.
Result- Percentage purity of unknown crystalline
FAS given in bottle B is found to
be ...........%.
Some
Imp. Reagents.
1)
Shiff’s reagent - 1 gm Pararosauiline hydroxide in 100 ml water. Heat, Coll and
then filter the solution pass SO2 gas in filtrate and dil. the solution to 1
lit. so that pink colour disappears.
2)
Cerric Ammonium - 100 gm Cerric ammonium nitrate in 250 ml HNO3 solution.
3)
Sodium Nitroprusside - Take 1 gm reagent in 200 ml distilled water.
4)
Tollen’s Reagent - 2 ml 5% AgNO3 + 1 drop NaOH, mix well and add NH4OH so that ppt will disolve.
5)
2,4-dinitrophenyl hydrazine solutoin- mix (4 gm sub + 20 ml conc. H2SO4) and ( 40 ml spirit + 40 ml dist. water)
6)
Phenylhydrazine solution - 20 gm phenyl hydrazine in 20 ml glacial acetic acid
in 200 ml dist water.
7)
Mollisch’s reagent - 10 gm -Naphthol in 90 ml spirit.
8)
Fehling’s solution (A) - 34.8 CuSO4 in 500 ml dist. water
and same drops of dil. H2SO4
Fehling’s solution (B) - 164 gm Rocholla salt and 50 gm NaOH in
500 ml dist. water.
Appendix - 4
Primary
treatment which can be done in the lab
the
first aid box should be in the lab. A general first aid has following
medicines- Dettol, Glycerine, Burnol, 1%
Acetic acid, 1 % and 8% boric acid, cotton, bandadge.
Acidentally
if any mishappens ocurs in the lab inform your teacher.
Following
is the primary treatment for the acident occur in the lab.
1)
On burning -
a)
by flask (fine burnign)- Rub 8% NaHCO3 solution on that burnign
part.
b)
With hot water - use Acroflavin.
c)
By Br2 -8% NaHCO3
d) By Na metal - Wash
with H2O and add 1% acetic acid then apply olive
oil.
e) by acid - wash with cold water and then apply 8% NaHCO3 solution then again wash with acroflavin.
f) by bare - wash with cold water immediately and then wash
with 1% CH3COOH.
2) by inhaling any gas- Take the student to fresh air give
artificial resp. if the breathing stopped.
i) Do gangles with NaHCO3 solution which inhated
Cl2 or
Br2 gas.
ii) On inhaling excess of NH3, put chill water in the nose.
C) On Fire -
i) Use fire extinguisher
ii) Fold using thick blanket when fire to the colothes.
D) during Eye aecident
a) Br2 water in eyes- wash eyes with 1% of NaHCO3 solution and then
consult doctor.
b) Acid in eyes- Wash eyes with
1% of NaHCO3 solution and then wash with cold water.
c) Base in eyes - Wash eyes with cold water and then with 1%
with boric acid solution.
E) When chemical into the mouth-
i) wash the mouth with water and then do gargles with cold
water in care. when acid enters into mouth.
ii) In the care of base drink excess of water and then drink
milk.
