Chemistry Volumetric Lab
Chemistry Volumetric Lab
Chemistry Volumetric Lab
4
Date:
Determination of Calcium in Portland Cement
(Permanganometry)
Aim: To determine the amount of Calcium (as oxide) present in the given sample of
Portland Cement by using a standard solution of Potassium permanganate
Apparatus: Burette, Pipette, Conical flasks, Beakers, Volumetric flask, Measuring jar,
Distilled water bottle, Burette stand, Glazed tile and Fischer clamp.
Theory: Metals like calcium, copper, lead and zinc form sparingly soluble oxalates and
they can be determined by dissolving the washed precipitate in dilute sulphuric acid and
titrating with a standard potassium permanganate. This method is widely used for the
determination of calcium.
Calcium present in a solution is precipitated as its oxalate by the addition of
ammonium oxalate solution to a dilute hydrochloric acid of cement followed by 1:1
ammonia solution for neutralising the acid. The calcium oxalate precipitate is filtered
using Whatmann No. 42 filter paper and thoroughly washed with water. The calcium
oxalate precipitate is dissolved in dilute sulphuric acid, heated to 70-800 C and titrated
against a standard solution of potassium permanganate for the Determination.
In the above reaction, all the reactants and products are colourless except
potassium permanganate. Hence, after the completion of the reaction of peroxide with
permanganate the excess trace amount of permanganate imparts a pink colour to the
solution taken as the end point of the reaction.
Procedure: 10.0 ml of standard oxalic acid solution is pipetted out into a clean conical
flask carefully. To this 10.0 ml of 10N sulphuric acid solution and 40.0 ml of distilled
water are added with measuring jar. The contents of the conical flask are heated to 70-
800 C (when the solution just starts to boil) the hot solution is titrated with constant
thorough shaking with potassium permanganate solution from the burette until the colour
of the solution changes from colourless to pale pink by the addition of one drop of
potassium permanganate solution, which is the end point of the reaction. A number of
titrations are carried out until 2 or 3 concurrent readings are obtained. The results are
tabulated neatly in Table - I
Table – I
Standardisation of Potassium Permanganate Solution
Calculation:
Normality of standard oxalic acid solution = N1 (Given)
Volume of oxalic acid solution = V1 = 10.0 ml
Normality of KMnO4 solution = N2 = ?
Volume of KMnO4 solution = V2 = ml
V1 N1
Normality of KMnO4 solution (N 2 ) = ________
V2
Procedure:
10.0 ml of the above prepared cement solution is pipetted out into a clean conical
flask carefully. To this 10.0 ml of 10N sulphuric acid solution and 40.0 ml of distilled
water are added with measuring jar. The contents of the conical flask are heated to 70-
800 C and the hot solution is titrated with constant thorough shaking with potassium
permanganate solution from the burette in the cold until the colour of the solution changes
from colourless to pale pink by the addition of one drop of potassium permanganate
solution, which is the end point of the reaction. A number of titrations are carried out
until 2 or 3 concurrent readings are obtained. The results are tabulated neatly in Table-II
Table – II
Determination of Calcium as Calcium Oxide
S. Vol. of Cement Burette Reading (ml) Volume of
No solution Taken KMnO4
(ml) Initial Final consumed (ml)
1 10.0 0.0
2 10.0
3 10.0
4 10.0
5 10.0
Calculation:
Normality of KMnO4 solution = N2 (From part I) =
Volume of KMnO4 solution = V2 A = ml
Normality of Cement solution = N3 = ?
Volume of Cement solution = V3 = 10.0 ml
Precautions:
1. In the standardisation of KMnO4 and in the Determination of Calcium
oxide content in the sample of Portland cement the contents of the conical
flask should not be heated for a ling time as decomposition may occur.
2. All the other apparatus should be cleaned with tap water and wipe the
work bench dry with a waste cloth after completing the experiment.
3. The cement solution should be prepared accurately without any wastage
Apparatus: Burette, Pipette, Conical flasks, Beakers, Volumetric flask, Measuring jar,
Distilled water bottle, Burette stand, Glazed tile and Fischer clamp.
Theory: Hydrogen peroxide H2O2 is usually available in the form of solution containing
about 3.0%. 6.0%, 12.0% and 30.0% of hydrogen peroxide. It is usually marketed in
volume strength of 10.0, 20.0, 40.0 and 100.0 concentrations. This terminology is based
on the volume of oxygen liberated when the solution decomposes by boiling. Thus 1.0ml
of 20.0 volume strength of hydrogen peroxide will yield 20.0 ml of oxygen measured at
STP (00 C and 760mm)
H 2 O 2 O 2 2H 2e -
2KMnO4 3H 2SO 4 K 2SO 4 2MnSO4 3 H 2 O 5(O)
5H 2 O 2 5(O) 5H 2 O 5O 2
2KMnO4 5H 2 O 2 3H 2SO 4 K 2SO 4 2MnSO4 8 H 2 O 5O 2
Procedure: 10.0 ml of standard Mohr‟s salt or Ferrous sulphate solution is pipetted out
into a clean conical flask carefully. To this 10.0 ml of 10N sulphuric acid solution and
40.0 ml of distilled water are added with measuring jar. The contents of the conical flask
are titrated with constant thorough shaking with potassium permanganate solution from
the burette until the colour of the solution changes from colourless to pale pink by the
addition of one drop of potassium permanganate solution, which is the end point of the
reaction. A number of titrations are carried out until 2 or 3 concurrent readings are
obtained. The results are tabulated neatly in Table - I
Table – I
Standardisation of Potassium Permanganate Solution
Calculation:
Normality of standard Mohr‟s Salt solution = N1 (Given)
Volume of Mohr‟s salt solution = V1 = 10.0 ml
Normality of KMnO4 solution = N2 = ?
Volume of KMnO4 solution = V2 = ml
Procedure:
The hydrogen peroxide solution given in the 100.0 ml volumetric flask is diluted
up to the mark with distilled water and mixed thoroughly for complete homogenisation.
10.0 ml of this solution is pipetted out into a clean conical flask carefully. To this 10.0 ml
of 10N sulphuric acid solution and 40.0 ml of distilled water are added with measuring
jar. The contents of the conical flask are titrated with constant thorough shaking with
potassium permanganate solution from the burette in the cold until the colour of the
solution changes from colourless to pale pink by the addition of one drop of potassium
permanganate solution, which is the end point of the reaction. A number of titrations are
carried out until 2 or 3 concurrent readings are obtained. The results are tabulated neatly
in Table-II
Table – II
Determination of Hydrogen Peroxide
Calculation:
Normality of KMnO4 solution = N2 (From part I) =
Volume of KMnO4 solution = V2 A = ml
Normality of H2O2 solution = N3 = ?
Volume of H2O2 solution = V3 = 10.0 ml
Volume of Oxygen liberated by ’X’ grams of Hydrogen peroxide at STP (0O C and
760 mm):
Precautions:
1. All the apparatus should be cleaned with tap water and wipe the work
bench dry with a waste cloth after completing the experiment.
2. Hydrogen peroxide solution should be freshly prepared and the bottle
should be placed back in the refrigerator otherwise the contents will
decompose.
Apparatus: Burette, Pipette, Conical flasks, Beakers, Volumetric flask, Measuring jar,
Distilled water bottle, Burette stand, Glazed tile and Fischer clamp.
Theory: Zinc can be determined titrimetrically using a standard solution of EDTA and
Eriochrome Black-T as indicator. The indicator is yellow at pH=6.0 blue at pH=8-12 and
orange at pH=13.0. The titrations can be carried out at pH=10 by adding ammonium
chloride buffer solution using Eriochrome Black-T as indicator. The metal forms a wine
red complex with the indicator and turns to a clear blue colour at the end point.
2 2 2
Zn H Y ZnY 2H
2
NaOOCH2C CH2COOH
N CH2 CH2 N
HOOCH2C CH2COONa
(Di Sodium Salt of Ethylene Diamine Tetra Aceticacid)
Procedure: 10.0 ml of standard zinc sulphate solution is pipetted out into a clean conical
flask carefully. To this 20.0 ml of distilled water and 3 to 4 ml of ammonium hydroxide-
ammonium chloride buffer solution (pH=10.0) and 2-3 drops of Eriochrome Black-T
indicator are added. The contents of the flask are titrated with EDTA solution from the
burette until the colour changes from wine red to clear blue colour. by the addition of one
drop of EDTA solution. A number of titrations are carried out until 2 or 3 concurrent
readings are obtained. The results are tabulated neatly in Table - I
Table – I
Standardisation of EDTA solution using a standard solution of zinc sulphate
heptahydrate
Calculation:
Normality of standard ZnSO4.7H2O solution = N1 (Given)
Volume of ZnSO4.7H2O solution = V1 = 10.0 ml
Normality of EDTA solution = N2 = ?
Volume of EDTA solution = V2 = ml
Procedure:
Zinc Sulphate heptahydrate solution given in the volumetric flask is diluted up to
the mark and mixed well for complete homogenisation. 10.0 ml of this zinc sulphate
solution is pipetted out into a clean conical flask carefully. To this 20.0 ml of distilled
water and 3 to 4 ml of ammonium hydroxide-ammonium chloride buffer solution
(pH=10.0) and 2-3 drops of Eriochrome Black-T indicator are added. The contents of the
flask are titrated with EDTA solution from the burette until the colour changes from wine
red to clear blue colour. by the addition of one drop of EDTA solution. A number of
titrations are carried out until 2 or 3 concurrent readings are obtained. The readings are
tabulated in Table-II
Table – II
Determination of percentage or the amount of available Chlorine in Bleaching
Powder
Calculation:
Normality of EDTA solution = N2 (From part I) =
Volume of EDTA solution = V2 A = ml
Normality of ZnSO4.7H2O solution = N3 = ?
Volume of ZnSO4.7H2O solution = V3 = 10.0 ml
NO2
Expt. No. 7
Date:
Determination of Total Hardness of Water
(Complexometry)
Aim: To determine the total hardness of the given water sample titrimetrically using a
standard solution of EDTA.
Apparatus: Burette, Pipette, Conical flasks, Beakers, Volumetric flask, Measuring jar,
Distilled water bottle, Burette stand, Glazed tile and Fischer clamp.
EDTA forms complexes with calcium and magnesium wht the pH of the solution is
around 9.5 – 10.5 and to maintain the pH between this range a buffer solution of
Ammonium hydroxide and ammonium chloride is used. The complexes of calcium and
magnesium with EDTA are colourless hence an indicator is necessary to locate the end
point. Eriochrome Black-T is used as indicator, which forma an unstable wine red
complex with Calcium and Magnesium. The calcium complex is first formed with
EDTA, but the colour change does not occur until all the magnesium is also converted
into a complex. It is thus possible to determine the total amount of these metals present in
the water sample and the total hardness of water can be calculated. Calcium itself does
not give a satisfactory end point colour change of the indicator unless the water sample
also contains magnesium. Assuming that the water sample contains only calcium, 2 or 3
drops of Magnesium-EDTA complex is added as a precautionary measure. When all the
calcium and magnesium are removed by EDTA, the free indicator imparts a blue colour,
the end point of the reaction.
NaOOCH2C CH2COOH
N CH2 CH2 N
HOOCH2C CH2COONa
(Di Sodium Salt of Ethylene Diamine Tetra Aceticacid)
Procedure: 10.0 ml of standard zinc sulphate solution is pipetted out into a clean conical
flask carefully. To this 20.0 ml of distilled water and 3 to 4 ml of ammonium hydroxide-
ammonium chloride buffer solution (pH=10.0) and 2-3 drops of Eriochrome Black-T
indicator are added. The contents of the flask are titrated with EDTA solution from the
burette until the colour changes from wine red to clear blue colour. by the addition of one
drop of EDTA solution. A number of titrations are carried out until 2 or 3 concurrent
readings are obtained. The results are tabulated neatly in Table - I
Table – I
Standardisation of EDTA solution using a standard solution of zinc sulphate
heptahydrate
Calculation:
Normality of standard ZnSO4.7H2O solution = N1 (Given)
Volume of ZnSO4.7H2O solution = V1 = 10.0 ml
Normality of EDTA solution = N2 = ?
Volume of EDTA solution = V2 = ml
Procedure:
100 ml of the hard water sample is accurately measured into a clean conical flask.
To this 3 to 4 ml of ammonium hydroxide-ammonium chloride buffer solution (pH=10.0),
2 drops of 0.1M Mg-EDTA complex are added. The complex helps to get a clear end
point. Now add 2-3 drops of Eriochrome Black-T indicator and the contents of the flask
are titrated with EDTA solution from the burette until the colour changes from wine red
to clear blue colour by the addition of one drop of EDTA solution. A duplicate titration is
carried out and the average titre value is determined. The readings are tabulated in Table-
II
Table – II
Determination of percentage or the amount of available Chlorine in Bleaching
Powder
Calculation:
1,000 ml of 0.01M EDTA = 1.0 g of CaCO3
Ta ml (average titre value) of a M EDTA =
Ta aM Ta aM
1 g of CaCO 3
1000 0.01 10
Ta aM
„W‟ ml or g of water sample taken = g of CaCO 3
10
1,000,000 Ta aM
1,000,000 ml or g of water = g of CaCO 3
W 10
Where „W‟ is the amount of water taken, Ta is the average titre value and aM is the
molarity of EDTA solution
Precautions:
1. In the standardisation of EDTA solution, the burette should be rinsed
thoroughly with distilled wate and small quantity of EDTA solution
respectively.
2. After each titration the conical flask should be properly cleaned and rinsed
with distilled water before doing another titration
3. It is enough to add 20.0 ml of distilled water to the contents of the conical
flask before commencing a titration.
4. All the other apparatus should be cleaned with tap water and wipe the
work bench dry with a waste cloth after completing the experiment.
NO2
Expt. No. 8
Date:
Determination of Chromium (VI) in Potassium Dichromate
Aim: To determine the amount Chromium (VI) present in the given solution Potassium
Dichromate by titrating against a standard solution of Ferrous Iron or Mohr‟s salt.
Apparatus: Burette, Pipette, Conical flasks, Beakers, Volumetric flask, Measuring jar,
Distilled water bottle, Burette stand, Glazed tile and Fischer clamp.
Procedure: 10.0 ml of standard Mohr‟s salt or Ferrous sulphate solution is pipetted out
into a clean conical flask carefully. To this 10.0 ml of sulphuric acid – phosphoric acid
mixture solution and 40.0 ml of distilled water are added with measuring jar. Two drops
of diphenylamine indicator are added and the contents of the conical flask are titrated
with constant thorough shaking with standard potassium dichromate solution from the
burette until the colour of the solution changes from colourless –pale green – dark green –
bluish green – purple violet. The colour change from bluish green to purple or bluish
violet colour should occur by the addition of one drop of dichromate solution A number
of titrations are carried out until 2 or 3 concurrent readings are obtained. The results are
tabulated neatly in Table - I
Table – I
Standardisation Mohr’s salt solution against a standard solution of Dichromate
Calculation:
Normality of standard K2Cr2O7 solution = N1 (Given)
Volume of K2Cr2O7 solution = V1 = ml
Normality of Mohr‟s Salt solution = N2 = ?
Volume of Mohr‟s Salt solution = V2 = 10.0 ml
Procedure:
Potassium Dichromate solution given in the 100.0 ml volumetric flask is diluted
up to the mark with distilled water and mixed thoroughly for complete homogenisation.
The burette is thoroughly cleaned with tap water, rinsed with small quantity of distilled
water and unknown dichromate solution from the volumetric flask respectively. Now fill
the burette with unknown dichromate solution. 10.0 ml of the standard Mohr‟s salt
solution (standardised in part I) is pipetted out into a clean conical flask carefully. To this
10.0 ml of sulphuric acid – phosphoric acid mixture solution and 40.0 ml of distilled
water are added with measuring jar. After adding two drops of diphenylamine indicator,
the contents of the conical flask are titrated with potassium dichromate solution from the
burette until the colour of the solution changes from colourless –pale green – dark green –
bluish green – purple violet by the addition of one drop of potassium dichromate solution.
A number of titrations are carried out until 2 or 3 concurrent readings are obtained. The
readings are tabulated in Table-II
Table – II
Determination of Ferrous Iron or Mohr’s Salt
Calculation:
Normality of Mohr‟s salt solution = N2 (From part I) =
Volume of Mohr‟s salt solution = V2 A = 10.0 ml
Normality of K2Cr2O7 solution = N3 = ?
Volume of K2Cr2O7 solution = V3 = ml
Precautions:
1. The standard Potassium Dichromate solution and the diluted solution of
the unknown Potassium dichromate solution given in a 100.0ml volumetric
flask are to be taken in the Burette for part-I and Part-II
2. All the other apparatus should be cleaned with tap water and wipe the
work bench dry with a waste cloth after completing the experiment.
Diphenyl benzidine
H H
N N
Diphenyl benzidine
N N
Note:
The above method can be adopted to determine the Chromium present in Steel.
Cr(III) present in steel should be oxidised to Cr(VI) before the Determination.
Though the reaction is between the Ferrous Iron or Mohr‟s salt and Potassium
dichromate, it cannot be used to determine Ferrous Iron or Mohr‟s salt as Potassium
dichromate is a better primary standard than Ferrous Iron or Mohr‟s salt.