1.
Normality of potassium permanganate in the sour medium
is equal 0,02200 mol/L. Calculate titer of this solution on: Í2Ñ2Î4; Fe; Í2Î2?
2.
To calculate molarity, normality, titer and titer on Fe (II) and As
(III) of potassium bichromate solution which are received dissolution shot of 2,4515 g potassium bichromate in 500
mL of water.
3.
Which volume of 0,1 mol/L solution potassium
permanganate it is necessary to take for preparation of 100 mL solution with normality of 0,05 mol/L?
4.
Calculate shot of sodium oxalate for preparation of
100 mL standard solution with normality of 0,05 mol/L which is used for
standardization of potassium permanganate solution. Calculate titer of sodium oxalate solution.
5.
Calculate weight of potassium bichromate shot for
preparation of 250 mL a solution of with normality 0,05 mol/L.
6.
What mass part of iron in a preparation if after shot
dissolution (weight 0,1400 g) in sulphatic acid without air access on titration of the
received solution spends 5,85 mL of potassium permanganate solution with normality 0,1000 mol/L?
7.
How many grammes of calcium contain in 250,0 mL of CaCl2
solution, if after addition 40,00 mL of 0,1000 mol/L (NH4)2C2O4
to 25,00 mL of this solution and separation of
CaÑ2O4 precipitate,
on titration of ammonium oxalate excess are spent 15,00 mL of 0,02000 mol/L (normality) solution of KMnÎ4?
8.
For permanganatometric definition of magnesium peroxide MgÎ2 was prepared 10 mL
of solution in which contain 0,2045 g, on titration of the prepared solution
have spent 19,75 mL of a standard potassium permanganate solution with titer on magnesium peroxide 0,002816 g/mL. Calculate
weight and mass fraction magnesium peroxide in a preparation.
9.
For an establishment of titer sodium thiosulphate is took of shot 0,1125 g of copper to which add
solution of KI. Iodine which was allocated, an investigated solution is titrated by sodium thiosulphate (18,99 mL). Calculate:
titer
of
this solution; titer of solution Na2S2O3 on Cu.
10. Which shot of K2Cr2O7
is necessary to take for an establishment of titer of 0,1 mol/L Na2S2O3
solution if for preparation of a primary standard K2Cr2O7
solution is a volumetric flask (200 mL) and pipette for selection of aliquot (10.00 mL). The
recommended volume of Na2S2O3 for titration of
iodine which will be allocated, spend 25,00 mL.
11. How many grammes of
Cl2 contain in 1 L of chloric water if on titration of iodine which
is allocated afret action of 25 mL KI, 20,10 mL of 0,1100 mol/L sodium
thiosulphate solution are used?
12. How many grammes
HCl contain in 250 mL of a solution chloridic acids if 24,00 mL of a
solution are spent for titration of iodine which was allocated after addition
25,00 mL of mix KIO3 + KI solution of 0,02100 mol/L sodium thiosulphate?
13. To define a mass
fraction of ascorbic acid, if for titration of 0,3568 g shot is spent 19,95 mL
of 0,1008 mol/L iodine solution (
). Equation of reaction:
ANSWERS
TON THE SELF-ASSESSMENT
Tests: 1. Ñ, 2. E., 3. B., 4. D.
Tasks: 1., 2., 3., 4., 5., 6., 7., 8., 9., 10., 11.,
12., 13., 14.
REFERENCES:
1. The lecture’s material.
2. David Harvey. Modern Analytical Chemistry //
www.mhhe.com
METHOD
OF IMPLEMENTATION OF PRACTICAL WORK
Work 1. Preparation and
standardization of a solution of 0,02 mol/L (0,1 N) potassium permanganate.
Dissolve
3.2 g of potassium permanganate
in 1000 ml of water, heat on
a water bath for 1 hour, cool and filter
through a sintered-glass filter.
Ascertain its exact concentration immediately before
use in the following manner. To 20 ml of the solution add 2 g
of potassium iodide and 10 ml of
1M sulphuric acid and titrate
with 0.1M sodium thiosulphate VS using 1 ml of starch solution, added
towards the end of the titration, as indicator.
Each ml of 0.1M sodium thiosulphate VS is equivalent to 3.161 mg of KMnO4.
Store protected from light.
Concentration of secondary standard solution of
KMnO4 calculates using this formula:
Work 2. Definition of hydrogen perioxide in drugs.
Definitions
is based on reaction
5H2O2+2MnO4- + 6H+ = 5O2+2Mn2++ 8H2O
Apparently from the equation, H2O2
in this reaction is a reducer and is oxidised to oxygen:
H2O2
- 2e = O2+2H+
Accordingly:
g/mol
Dilute 10.0 g to 100.0 ml with water R. To 10.0
ml of this solution add 20 ml of dilute sulphuric
acid R. Titrate with 0.02 M potassium permanganate until a pink colour
is obtained.
1 ml of 0.02 M potassium permanganate is
equivalent to 1.701 mg of H2O2 or 0.56 ml of oxygen.
Content of hydrogen perioxide in drugs calculates using this formula:
Hydrogen
peroxide solution (3 per cent) contains not less than 2.5 per cent m/m and not more than 3.5 per cent m/m of
H2O2 (Mr 34.01).
Work 3. Definition the
maintenance of ascorbic acid in a dragee of 0,05 ascorbic acid
0,74 g a powder of
the pounded dragees place in a conic flask spaciousness of 250 ml, add 80 ml of
water, free from carbon dioxyde and 10 ml of sulphatic acid,
dissolve, then add 1 ml of 1 % starch solution
and titrate by 0,05 mol/l iodine solution before
reception of proof blue-violet colouring.
This titration
repeats three times. By results of titrations define the maintenance of ascorbic
acid in a drug, considering on average weight of a dragee.
Content of ascorbic acid in dragee calculates using this formula:
The content of acid
ascorbic in one dragee should be 0,045 – 0,055 g.
BASIC LEVEL OF KNOWLEDGE AND SKIILS
A STUDENT MUST KNOW:
1.
Essence
of redoxmetry, types of reactions which are applied, requirements to them.
2. Classification of methods redox titration.
3.
An
essence of permanganatometry, dichromatometry, iodometry, iodimetry, iodatometry and
their application.
A STUDENT
MUST BE ABLE:
1.
To
prepare and standardise of solutions potassium permanganate, potassium
bichromate, iodine, sodium thiosulphate, potassium
iodate.
2.
To
define the contain of reducers and oxidizers by permanganatometry, dichromatometry,
iodometry, iodimetry, iodatometry.
Prepared by Associate Prof. Vronska L.V., Mykhalkiv M.M.