elements of vib-viib groups
TRANSCRIPT
Inorganic Chemistry DepartmentGeneral and Inorganic Chemistry
In specialty 226 Pharmacy, industry pharmacy
Iryna VEDERNYKOVA,Doctor of Pharmaceutical Sciences, Professor
Elements of VIB-VIIB groups
1. Some properties of elements VIB group.2. Chromium. Chromium compounds. Chromium (III) cation and its
properties. Chromate and dichromate. Complex compounds of Chromium.
3. The Qualitative Reaction for Compounds Which Contain elements of VIB group.
4. Biological role compounds of elements VIB groupand their application in medicine.
5. Some properties of elements VIIB group.6. Manganese. Manganese compounds. Manganese (II) cation and its
properties. Permanganate ion.7. The Qualitative Reaction of Manganese (II) and permanganate ion.8. Biological role compounds of elements VIIB group
and their application in medicine.
Plan of Lecture
2
Actuality of theme
3
Biologically active substances of elements of VIB and VIIB groups are ofgreat importance in pharmacy and medicine.
Aim: Depending on the electronic structure of elements of VIB and VIIBgroups, their properties and the place they occupy in medicine and pharmacyare determined.
Specific goals:• Be able to write electronic formulas of elements of VIB and VIIB groups
in various degree of oxidation.• Know the ways to get and use them in medicine.
Theoretical questions for individual work
4
Tungsten and Molybdenum. Properties of simple substancesand their compounds.
Technetium and Rhenium. Properties of simple substancesand their compounds.
➢ General and inorganic chemistry: Textbook for students of higher schools Ye.Ya.Levitin, I.O.Vedernikova.– Kharkiv:Publishing House of NUPH :Golden Pages,2009. – 360 p.
➢ General and Inorganic Chemistry Laboratory Practicum / Ye.Ya. Levitin, I.O. Vedernikova, L.Yu. Klimenko, O.S. Kryskiv. – Kharkiv, 2020. – 106 p.
➢ General and inorganic chemistry: The lecture course for the students of pharmaceutical universities and pharmaceutical faculties of higher medical education / Ye.Ya. Levitin, I.O. Vedernikova, L.Yu. Klimenko, O.S. Kryskiv. – Kharkiv: NUPH Publishers, 2020. – 123 p.
➢ The collection of theoretical questions and tests in inorganic chemistry:for the students of higher school. / Ye.Ya.Levitin, I.O.Vedernikova.– Kharkiv: NUPH Publishers, 2007. – 76 p.
Bibliographical Guidance
5
The Elements of VIB Group
Chromium Cr24 [Ar] 4s13d
5
Molybdenum Mo42 [Kr] 5s
14d
5
Wolfram (Tungsten) W74 [Xe] 4f14
6s25d
4
1
• d- sublevels are completed with valence electrons, these elements are
the d-electronic families members
• these elements have 6 valence electrons, they are the elements
of VI-th group. The highest oxidation state is + 6
• chromium and molybdenum have only one electron on s-sublevel due
to symmetry rule (the power condition of an atom is considered more
slayable when the sublevel is filled completely or half )
Chromium
Chromium was discovered by Louis-Nicholas Vauquelin at 1797 in France.
Origin of name: from the Greek word "chroma"meaning "colour", named for the many coloured compounds known for chromium.
Brief description:
2
Chromium is a lustrous, brittle, hard metal. Its colour is silver-gray and it can be highly polished.
It does not tarnish in air, when heated it borns and forms the green chromic oxide. Chromium is unstable in oxygen, it immediately produces a thin oxide layer that is impermeable to oxygen and protects the metal below.
Occurence of chromium
Chromium is found as chromite
FeCr2O4 ore.
Siberian red lead - crocoite,
PrCrO4 is a chromium ore prized
as a red pigment for oil paints.
3
Molybdenum 2
Molybdenum is a silvery-white,
hard, transition metal. Molybdenum is
used in alloys, electrodes and
catalysts. The World War 2 German
artillery piece called "Big Bertha"
contains molybdenum as an essential
component of its steel.
Biological role:
molybdenum is a necessary element,
apparently for all species. Only very small
amounts are required. Molybdenum plays a role in nitrogen fixation, (a process
by which the normally unreactive nitrogen gas is turned into other compounds)
enzymes, and nitrate reduction enzymes.
Hazards and risks associated with molybdenum:
its compounds are encountered relatively rarely by most people. Unless known
otherwise, all molybdenum compounds should be regarded as highly toxic and
as teratogenic.
Tungsten 2
Pure tungsten is a steel-gray to tin-white
metal. Tungsten has the highest melting point
and lowest vapour pressure of all metals, and
at temperatures over 1650°C has the highest
tensile strength. It has excellent corrosion
resistance and is attacked only slightly by
most mineral acids.
Biological role:
tungsten has a limited biological role.
A number of enzymes (oxidoreductases) employ
tungsten in a way related to molybdenum,
(using tungsten.pterin complex).
The structure of a tungstoenzyme aldehyde ferredoxin oxidoreductase is known.
Hazards and risks associated with tungsten: tungsten metal does not normally
cause problems but all tungsten compounds should be regarded as highly toxic.
The metal dust presents a fire and explosion hazard.
Chromium compounds4
Conclusion:
0, +3, +6 are the most typical for chromium.
The o.s. increases the acidic properties increase
+2
0
+1
+3
+4
+5
+6
oxidation state
Cr simple compound, [Cr(CO)5] pentacarbonylchromium
CrO, CrCl2
Cr2O3, Cr(OH)3, Fe(CrO4)2 iron (II) metachromite
CrO3, K2CrO4
The preparation of compounds of chromium
(NH4)2Cr2O7 →
Cr + H2SO4 (dilute) →
Cr2O3 + N2 + 4H2O
Cr2O3
2Cr + 6H2SO4(conc.) = Cr2(SO4)3 + 3SO2 + 6H2O
Under the heating!
CrSO4 + H2
Chromium III oxide and hydroxide5
(NH4)2Cr2O7 → Cr2O3 + N2 + 4H2OThe reaction of de-combination of orange powder of ammonium
dichromate gives the green powder of chromium (III) oxide
Cr2(SO4)3 + 6NaOH → 2Cr(OH)3 + 3Na2SO4
2Cr3++3SO42- + 6Na++ 6OH- → 2Cr(OH)3 + 6Na+ + 3SO4
2-
Cr3+ + 3OH- → Cr(OH)3
The dark-green chromium (III) hydroxide precipitate is produced
Cr(OH)3 + 3NaOH → Na3[Cr(OH)6]
Cr(OH)3 + 3HCl + 3H2O → [Cr(H2O)6]Cl3
sodium hexahydroxochromate(III)
hexaaquachromium (III) chloride
Conclusion:
Chromium (III) oxide and hydroxide are amphoteric – react with acid and with base
The hydrolysis of chromium (III)
molecular equation: Cr2(SO4)3 + 3Na2S + 6H2O → 2Cr(OH)3(s) + 3H2S(g)
net ionic equation: 2Cr3+ + 3S2– + 6H2O → 2Cr(OH)3(s) + 3H2S(g)
6
Conclusion:
If salt is formed by the weak, insoluble basis and weak acid, unstable in a solution, the hydrolysis reaction proceeds up to the end (such salts do not exist in a solution and may be received only by thermal interaction of simple substances).
Irreversible hydrolysis (co-hydrolysis):
Conclusion:
Due to hydrolysis the solutions of chromium (III) salts have acidic medium
Indicator methyl-orange into these solution has pink color
The salts of chromium (III) undergoing hydrolysis. Under normal condition
they hydrolyse only at the thirst step
molecular equation: CrCl3 + H2O CrOHCl2 + HCl
net ionic equation: Cr3+ + H2O CrOH2+ + H+ pH<7
Aqua-complex Cr(III) has several hydrated-isomers:
[Cr(OH2)6]Cl3 is blue-violet color
[Cr(OH2)5Cl]Cl2 ·H2O is light-green
[Cr(OH2)4Cl2 ]Cl ·2H2O is dark-green
7Complex compounds of chromium (III)
The equilibrium between hydroxo- and aqua- complex Cr (III) can be
represented with a scheme:
OH_ H+
[Cr(OH2)6]3+ [Cr(OH)3(OH2)3] [Cr(OH)6]
3-
Conclusion:
Chromium (III) cation produces complex compounds with
coordination number c.n. = 6
Chromium VI oxide and hydroxide 8
K2Cr2O7 + H2SO4 → CrO3 + H2O + K2SO4
dark-red crystals
CrO3 + H2OH2CrO4 chromic acid
H2Cr2O7 dichromic acid
Electronic configuration of chromium in these compounds: Cr+6 [Ar] 3d04s0
Highest oxidation state, in the oxidation-reduction reaction – oxidazing agent:
CrO42- + 4H2O + 3ē → [Cr(OH)6]
3- + 2OH- E0 = - 1.216 V
Cr2O72- + 14H+ + 6ē → 2 Cr3+ + 7H2O E0 = 1.333 V
Conclusion:
Chromium IV oxide and hydroxides are acidic. Dichromate ion is a very strong oxidizing agent.
All the compounds of chromium IV are very toxic. They widely used like ox. agent in industry.
Potassium dichromate is used for qualitative identification of H2O2:
4H2O2 + K2 Cr2O7+ H2SO4 → 2CrO5 + K2SO4 + 5H2O
chromium (VI)
oxidediperoxides
O
O
O
OCr
O
Potassium chromate
K2CrO4 → 2K+ + CrO42-
Potassium dichromate
K2Cr2O7 → 2K+ + Cr2O72-
9Transformation chromate into dichromate
The salts of chromium in the solution can dissociate:
Conclusion:
The transformation of chromate ion into dichromate depends
on the value of pH
If pH<7 (acidic medium) the dichromate ion is stable
If pH>7 (basic or neutral medium the chromate ion is stable
molecular equation: 2K2CrO4 + H2SO4 K2Cr2O7 + K2SO4 + H2O
net ionic equation: 2CrO42- + 2H+ Cr2O7
2- + H2O
Equilibrium in the solution:
K2CrO4
K2Cr2O7
Oxidizing properties of dichromate ion
3NaNO2 + K2Cr2O7 + 4H2SO4 = 3NaNO3 + Cr2(SO4)3 + K2SO4 + 4H2O
+ 6ē + Cr2O72– + 14H+ 2Cr3+ + 7H2O 1 E0 = 1.33 V
– 2ē + HNO2 + H2O NO3– + 3H+ 3 E0 = 0.84 V
Cr2O72- + 14H+ + 3HNO3 + 3H2O = 2Cr3+ + 7H2O + 3NO3
- + 9H+
reducing agentoxidizing agent
5H+ 5H2O
E0cell = E0
ox. agent – E0red.agent = 1.33 – 0.94 = 0.39 V
if pH<7 chromium (III) is the product of reduction: Cr2O72- Cr3+
if pH ≥ then 7 the chromium (III) hydroxide is produced:
3(NH4)2S + K2Cr2O7 + H2O = 3S + 2Cr(OH)3 + 6NH3 + 2KOH
10
reducing agentoxidizing agent
Some compounds of chromium are insoluble
Two moles of Ag+ and one mole CrO42– ion appear in the saturated
solution for every of Ag2CrO4 dissolved.
2S S
Ag2CrO4 2Ag+ + CrO42–
The value of the solubility product constant of silver (I) chromate:
Ksp = 2.410-12
The expression of the solubility product constant of silver (I) chromate:
Ksp = [Ag+]2 [CrO42-] = (2S)2 S = 4S3
4S3 = 2.4 10-12 (molL-1); S = 8.43 10-5 (molL-1)
S(gL-1) = S(molL-1)M(Ag2CrO4) = 331.68.4310-5=2.7910-2(gL-1)
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molar solubility
PbCrO4 lead (II) chromate Ksp = 2.810-13
Ag2CrO4 silver (I) chromate Ksp = 2.410-12
BaCrO4 barium chromate Ksp = 1.610-10
The reaction of qualitative identification
of chromium compounds
Cr2O72- + 2Ba2+ + H2O 2 BaCrO4 + 2H+
12
barium chromate
lead (II) chromate
Usage: insoluble
barium and lead
(II) chromate both
find use as
yellow pigments
The reactions for chromate ion :
CrO42-+ Pb2+ PbCrO4
The reaction for chromium (III) :
2Na3[Cr(OH)6] + 3H2O2 = 2Na2CrO4 + 2NaOH
– 3ē + [Cr(OH)6]3– + 2OH– CrO4
2- + 4H2O 2
+ 2ē + H2O2 2OH– 3
2 [Cr(OH)6]3– + 4OH– + 3 H2O2 = 2CrO4
2- + 8H2O + 6OH–2OH-
oxid. agentreducing agent
Yellow color appear
Chromium usage are:
• in alloys such as stainless steel, • in chrome plating and in metal ceramics, • in metallurgy to impart corrosion resistance and a shiny finish,• as dyes and paints,as a catalyst in dyeing and in the tanning of leather;
Chromium is an essential tracemineral required for normal protein,fat and carbohydrate metabolism.Chromium works, in part, byactivating the hormone insulin.
13
The Elements of VIIB Group
Rhenium
Technetium
Manganese
[Xe] 4f14
6s25d
5
[Kr] 5s24d
5
[Ar] 4s23d
5
Re75
Tc43
Mn25
1
• d- sublevels are completed with valence electrons, these elements are
the d-electronic families members
• these elements have 7 valence electrons, they are the elements
of VII-th group. The highest oxidation state is +7
Manganese• is a chemical element,
designated by the symbol Mn.
• It has the atomic number 25. It is found as a free element in nature (often in combination with iron), and in many minerals.
• As a free element, manganese is a metal with important industrial metal alloy uses, particularly in stainless steels.
MnSO4
Manganese compounds 4
Conclusion: 0, +2, +4, +7 are the most typical for chromium.
The o.s. is increased the acidic properties is increased:
MnO is basic, MnO2 is amphoteric, Mn2O7 is acidic.
+2
0
+1
+3
+4
+5
+6
oxidation state
Mn simple compound, [Mn2(CO)10] decocarbonyldimanganese
MnO manganese (II) oxide, MnSO4
Mn2O3 manganese (III) oxide
Mn2O7, HMnO4 permanganic acid, KMnO4 potassium permanganate+7
K2MnO4 potassium manganate
MnO2 manganese (IV) oxide
Manganese II hydroxide5
Mn + 2HCl → MnCl2 + H2
MnCl2 + 2NaOH → Mn(OH)2 + 2NaCl
Mn2+ + 2Cl- + 2Na+ + 2OH- → Mn(OH)2 + 2Na+ + 2Cl-
Mn2+ + 2OH-→ Mn(OH)2
White manganese (II) hydroxide precipitate is produced
It can be produced in the
basic solution of Mn(II) salt:
MnCl2
The properties of manganese II hydroxide:
1) Mn(OH)2 + 2HCl → MnCl2 + 2H2O
2) Mn(OH)2 + NaOH
Conclusion:
Manganese (II) hydroxide has basic properties. It reacts with acid (1) and does
not react with base (2). This hydroxide can be reducing agent in the ORR (3).
3) Mn(OH)2 + O2 → MnO2 + H2O
2Mn(OH)2 + 4OH- + O2 + 2H2O 2MnO2 + 4H2O +4OH-
1O2 + 2H2O + 4ē 4OH-
2Mn(OH)2 + 2OH- - 2ē MnO2 + 2H2O4
2
Mn(OH)2 MnO2
The hydrolysis of manganese (II)6
Conclusion:
Due to hydrolysis the solutions of manganese (II) salts have acidic medium
Indicator methyl-orange into these solution has pink color
molecular equation: MnCl2 + H2O MnOHCl + HCl
net ionic equation: Mn2+ + H2O MnOH+ + H+ pH<7
The salts of manganese (II) undergoing hydrolysis. Under normal
condition they hydrolyse only at the thirst step
The reaction of dissociation:
MnCl2 → Mn2+ + 2Cl -
The reaction of hydrolysis:
Reducing properties of manganese (II)
E0 = 1.51V2– 5ē + Mn2+ + 4H2O MnO4¯ + 8H+
E0 = 1.449 V5+ 2ē + PbO2 + 4H+ Pb2+ + 2H2O
E0cell = E0
ox. agent – E0red.agent = 1.449 – 1.51 = – 0.061 V
7
reducing agentoxidizing agent
2MnSO4 + 5PbO2 + 6HNO3 = 2HMnO4 + 3Pb(NO3)2 + 2PbSO4 + 2H2O
4H+ 2H2O
5PbO2 + 20H+ + 2Mn2+ + 8H2O = 5Pb2+ + 10H2O + 2MnO4¯ + 16H+
Conclusion:
manganese (II) in the ORR is the reducing agent.
This is the reaction of qualitative identification of manganese (II) cation.
violet color appears
Potassium permanganate, KMnO4
is an important oxidizing agent.
For chemical analyses it is generally used in acidic solutions,
where it is reduced to colorless Mn2+:
E0 = 1.51 V
It is reduced to brown solid MnO2 in neutral solution:
E0 = 0.60 V.
It is reduced to green MnO42– manganate-ion in basic solution:
E0 = 0.56 V.
Potassium Permanganate: Structure and Formula
• Potassium permanganate is not as popular as other chemical compounds,
but we probably encounter it more often than we think.
• Potassium permanganate, also known as permanganate of potash or
Condy's crystals
The physical state of potassium permanganate
is an odorless solid,
and they look like dark purple or bronze colored
crystals.
If we dissolve these
crystals in water, the
solution becomes purple in
color.
Potassium permanganate
is able to oxidize many
substances, so it is very
well known as a strong
oxidizing agent, a
substance that accepts or
takes electrons from other
substances.
Potassium permanganate
is a chemical compound
consisting of two ions:
a potassium ion and a
permanganate ion.
Uses Of Potassium Permanganate
Potassium permanganate has various uses in various fields,
such as
➢ Purifying water.
➢ Creating an antiseptic solution.
➢ As an anti-fungal treatment for the hands and feet.
➢ As a cholera disinfectant
➢ Marking snow as an emergency signal.
➢ General disinfectant agent
Here Are Some Essential Uses Of
Potassium Permanganate.
1. Skin Infections :
Potassium Permanganate Treats Many Skin
Infections, Including Eczema, Dermatitis
And Acne.
2. Water Treatment :
Having A Strong Oxidizing Capacity, It Is
Ideal For Use In Water Treatment.
3. Fungal Infections :
Potassium Permanganate Foot Soaks
Treat Fungal Infections Such As
Athlete's Foot.
4. Fish Treatment :
Potassium Permanganate Can Be Used
To Treat Parasites On Individual Fish.
5. It Is Also Used As An Oxidizing Agent In Many
Chemical Reactions In Laboratories And Industry.
6. The Florists Use It For Making The Flowers
Look Fresh For A Longer Time.
7. Industrial And Chemical Uses :
It Is Used For Industrial Cleaning,
Bleaching, And Tanning.
Oxidizing properties of permanganate ion8
KMnO4 → K+
+ MnO4¯
Potassium permanganate dissociates in the water solution:
The electronic configuration of manganese
in the permanganate ion is: Mn+7 [Ar] 3d0 4s0
permanganate ion
MnO4¯ pH =7
Mn2+
MnO2
MnO4
2¯
in the acidic solution manganese (II) cation
is produced (MnSO4)
in the neutral solution the brawn precipitate of
manganese (IV) oxide is produced
in the basic solution manganate ion
is produced (K2MnO4)
Conclusion:
permanganate ion in the ORR is the oxidizing agent, the product of its reduction
depend on the type of solution
4521.01.2021
- 2ē10
5H2O2 + 2 MnO4- + 16 H+ = 5O2+ 10H+ + 2 Mn2+ + 8 H2O
O2
+ 5ē
H2O2
+ 4 H2O
5
2
H2O2 + KMnO4 + H2SO4 = O2 + MnSO4 + K2SO4 + H2O
+ 2H+
+ 8H+MnO4- Mn2+
6
5 2 3 5 2 8
Na2SO3 + KMnO4 + H2O = Na2SO4 + MnO2↓ + KOH+4 +7 +6 +4
MnO4- ↔
↔
MnO2
SO32- SO4
2- + H2O+ 2OH-
+ 2H2O + 4OH-
-2ē
+3ē
3
2
3SO32- + 6OH- + 2MnO4
- + 4H2O = 3SO42- + 3H2O + 2MnO2 + 8OH-
2
2 23 3 2
Na2SO3 + KMnO4 + KOH = Na2SO4 + K2MnO4↓ + H2O+4 +7 +6 +6
SO32- SO4
2- + H2O+ 2OH- ↔-2ē
MnO4- MnO4
2-↔+ē 2
1
SO32- + 2OH- + 2MnO4
- = SO42- + H2O + 2MnO4
2-
2 22
Reactions of potassium permanganate9
2KMnO4→ K2MnO4 + MnO2 + O2
The reaction of thermal decomposition is the method
of oxygen production in the laboratory:
Potassium manganate is not stable.
It is disproportionate:3K2MnO4 + 2H2O → 2KMnO4 + MnO2 + 4KOH
green color brown precipitate appears
+6 +7 +4
Manganese (VII) oxide is produced under the reaction
of potassium permanganate with acid:
2KMnO4 + H2SO4 → Mn2O7 + K2SO4 + H2O
The water solution of Mn2O7 is a very strong permanganic acid HMnO4,
the maximal concentration of this solution is 20%
Conclusion
• Manganese is used most commonly in steel
production to help improve strength, durability,
and toughness.
• It can be used in medicine to help support the
immune system, regulate your blood sugar, and
maintain bone regulation and reproduction.
• It is also used in gasoline to reduce engine
knock, and is used in alkaline batteries.
Thank you
for
attention!
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