Chuong 2HIDRO VA NUOC

-Hóa học của hidrua cộng hóa trị phụ thuộc mạnh vào bản chất nguyên tố liên kết với H. -Liên kết H-X trong một nhóm hơi giảm khi đi từ trên xuống; trong một chu kỳ nói chung tăng khi đ[r]

Department of Inorganic Chemistry - HUT

CHƯƠNG II

HYDRO VÀ NƯỚC

Hidro

Cấu tạo ngun tử Tính chất lý học Tính chất hóa học

Trạng thái thiên nhiên phương pháp điều chế Hidrua nguyên tố

Hidrua ion

Hidrua cộng hóa trị Hidrua kiểu kim loại Nước

Tính chất lý học Tính chất hóa học

Trạng thái thiên nhiên phương pháp tinh chế Sự gây ô nhiễm môi trường nước

1 H – e = H+ ΔHo = 1312 kJ/mol

2 H + e = H- ΔHo = -67 kJ/mol

3 Tạo nên cặp e chung cho liên kết cộng hóa trị

H giống kim loại kiềm khả e thành cation khác ở: -Năng lượng ion hóa lớn gấp vài ba lần so với kim loại kiềm.

-Proton bé nhiều so với nguyên tử (1.6-1.7.10-5 Å << 1.2 Å) mang điện tích dương  làm

nhiễu loạn đám mây e nguyên tử xung quanh.

-Proton khơng thể tồn mà kết hợp với nguyên tử hay phân tử khác, H3O+

H giống halogen khả nhận e thành ion H- có đặc điểm:

-Ái lực e H gần 1/5 so với lực e halogen. -Ion H- có cấu trúc e He (1s2)

-Ion H- tự có khả tồn hidrua muối KH, CaH

H có vị trí đặc biệt bảng hệ thống tuần hồn ngun tố hóa học H vừa giống-khác với kim loại kiềm halogen

H có đặc điểm mà ngun tố khác khơng có (do chất proton không

Occurrence and Abundance:

Occurrence and Abundance:

Elemental Composition of the Sun & the Universe

Elemental Composition of the Sun & the Universe

Sun

Sun UniverseUniverse

Hydrogen

Hydrogen 92.5 %92.5 % 90.87 % 90.87 %

Helium

Helium 7.3 %7.3 % 9.08 % 9.08 % All Others

All Others 0.2 %0.2 % 0.05 % 0.05 %

Elemental Composition of the Earth’s Crust (ppm mass)

Elemental Composition of the Earth’s Crust (ppm mass)

O - 455 000

O - 455 000 Mg - 27 640Mg - 27 640

Si - 272 000

Si - 272 000 Na - 22 700 Na - 22 700

Al - 83 000

Al - 83 000 K - 18 400 K - 18 400 Fe - 62 000

Fe - 62 000 Ti - 6320 Ti - 6320 Ca - 46 600

Elemental Composition of the Human Body:

Elemental Composition of the Human Body:

By Atoms

By Atoms By MassBy Mass

H - 63.0 %

H - 63.0 % 10.0 %10.0 %

O - 25.5 %

O - 25.5 % 64.6 %64.6 %

C - 9.5 %

C - 9.5 % 18.0 %18.0 %

N - 1.4 %

N - 1.4 % 3.1 % 3.1 %

Hydrogen also occurs in very large

Hydrogen also occurs in very large

quantities in the ocean and is present in

quantities in the ocean and is present in

more compounds than any other element.

H

H22

-C-C-MH

MHxx

HX HX

H H22OO

-C-C C-OH

-C-OH M + H

M + H22OO

NH NH33

N2 M

X2 O2

MxOy

C

=

O

1671 - Robert Boyle -

1671 - Robert Boyle - Noted a flammable gas Noted a flammable gas formed when iron was reacted with sulfuric acid.

formed when iron was reacted with sulfuric acid.

1766 - Henry Cavendish -

1766 - Henry Cavendish - Reacted acids with Fe, Reacted acids with Fe, Zn, and Sn and, thus, established the true

Zn, and Sn and, thus, established the true

properties of the element.

properties of the element.

1781 - Henry Cavendish -

1781 - Henry Cavendish - Showed quantitatively Showed quantitatively that water was formed when hydrogen was burned

that water was formed when hydrogen was burned

with oxygen, proving that water was

with oxygen, proving that water was NOTNOT an an element.

element.

1783 - Antoine Lavoisier -

1783 - Antoine Lavoisier - Proposed the name Proposed the name “hydrogen” from the Greek for “water former”.

Department of Inorganic Chemistry - HUT

Main article: Isotopes of hydrogen

iso NA half-life DM DE (MeV) DP

1H 99.985% H is stable with neutrons 2H 0.0115% H is stable with neutrons

3H trace 12.32 y β− 0.019 3He

Historical information

Discovered by: Henry Cavendish (1731-1810)

Discovered at: London, England

Discovered when: 1766

Molecular Properties of Hydrogen:

Molecular Properties of Hydrogen:

Over 40 Forms of Hydrogen Exist Over 40 Forms of Hydrogen Exist

-H, H

H, H22 H H++, H, H , H, H 2

2++, H, H33++, D, D, D, D22, D, D++, D, D ,,

HD, HT, DT, T, T

HD, HT, DT, T, T22, nuclear spin isomers, etc., nuclear spin isomers, etc. Isotopes of Hydrogen -

Isotopes of Hydrogen - A Protium

-A Protium - 11HH 1 P1 P++

B

B DDeuterium -euterium - 22HH 1 P1 P++ + n + n00

C

C TTritium -ritium - 33HH 1 P1 P++ + n + n00

(99.986 %)

(99.986 %)

(0.014 %)

(0.014 %)

(7 x 10

Physical Properties:

Physical Properties: HH22 D D22 TT22

Atomic Mass, u

Atomic Mass, u 1.0078 1.0078 2.0141 3.0160 2.0141 3.0160 Freezing Point,

Freezing Point, ooCC -259.0 -259.0 -254.3 -252.4 -254.3 -252.4

Boiling Point,

Boiling Point, ooCC -252.6 -252.6 -249.3 -248.0 -249.3 -248.0

Bond Length, pm

Bond Length, pm 74.14 74.14 74.14 (74.14) 74.14 (74.14)



HHDissociationDissociation, kJ/mol 435.9, kJ/mol 435.9 443.4 446.9 443.4 446.9



HHFusionFusion, kJ/mol, kJ/mol 0.117 0.117 0.197 0.250 0.197 0.250



HHVaporizationVaporization, kJ/mol 0.904, kJ/mol 0.904 1.226 1.393 1.226 1.393

Vapor Pressure, torr 54 5.8

-Department of Inorganic Chemistry - HUT

Hidro Physical properties Phase gas

Density (0 °C, 101.325 kPa)0.08988 g/L

Melting point 14.01 (−259.14 °K C, −434.45 °F

)

Boiling point 20.28 (−252.87 °K C, −423.17°F

)

Triple point 13.8033 K, 7.042 kPa

Critical point 32.97 K, 1.293 MPa

Heat of fusion (H2) 0.117 kJ·mol−1

Heat of vaporization (H2) 0.904 kJ·mol−1

Heat capacity (25 °C) (H2)

Electronic Structure and Modes of Reaction:

Electronic Structure and Modes of Reaction:

Hydrogen has the simplest electronic structure of all

Hydrogen has the simplest electronic structure of all

elements It consists of a nucleus containing one proton

elements It consists of a nucleus containing one proton

and one electron in the 1s orbital.

and one electron in the 1s orbital.

+

Modes of Reactivity:

Modes of Reactivity:

1 By losing an electron to form a hydrogen ion, H

1 By losing an electron to form a hydrogen ion, H++..

Protons are extremely small Protons are extremely small

and, therefore, are

and, therefore, are VERYVERY

polarizing because they have a polarizing because they have a

very large

very large charge densitycharge density.. They associate strongly with They associate strongly with

molecules around them Thus, molecules around them Thus,

in water or in acids they form in water or in acids they form

the

2 By gaining an electron to form a hydride ion, H

2 By gaining an electron to form a hydride ion, H ..

-Hydride ions,

Hydride ions, H H , exist in the ionic, exist in the ionic

crystalline solids of some of the Groups 1 crystalline solids of some of the Groups 1

and metal hydrides Only the most

and metal hydrides Only the most elec- elec-tropositive

tropositive metals will react to form ionic metals will react to form ionic (

3 By forming an electron pair (covalent) bond with

3 By forming an electron pair (covalent) bond with

another atom.

another atom.

H • • Cl :

H • • Cl :

H : Cl :

H : Cl :

Non-metals and some

Non-metals and some metals form covalent metals form covalent hydrides.

Department of Inorganic Chemistry - HUT

Trạng thái thiên nhiên phương pháp điều chế

Laboratory routes to H2

In the laboratory, H2 is usually prepared by the reaction of acids on metals such as zinc

Zn + H+ → Zn2+ + H

Aluminum produces H2 upon treatment with acids but also with base: Al + H2O → Al(OH)3 + H2

Department of Inorganic Chemistry - HUT

Tính chất hóa học

Tính bền nhiệt Tính khử

Tính oxy hóa

2000

2 ( ) 2

K

H k    H 298 432 /

o

H kJ mol

 

H2 với vỏ e He nên bền nhiệt, khó phân hủy thành H Ở p = atm 2000 K, H2 phân hủy 0.1 %.

Ở 5000 K phân hủy đạt 95 %

Quá trình phân hủy phải thu nhiều nhiệt.

H – e = H+ ΔHo = 1312 kJ/mol 2( ) 2( ) 2 ( )

H k  F k  HF k

550

2 2 2

2 ( ) ( ) 2 ( ) 241 /

oC

o

H k O k H O k

H kJ mol

     

Phản ứng xảy nhiệt độ thường, không cần xúc tác. Hỗn hợp thể tích hidro flo nổ nhiệt độ thấp

Hỗn hợp không phản ứng nhiệt độ thấp lại nổ có lửa.

Khí hidro cháy êm dịu oxi tinh khiết  phản ứng tỏa nhiều nhiệt, lửa

đạt 2500 oC  ứng dụng làm đèn xì hidro-oxy để cắt kim loại, nấu chảy thạch anh,

Pt, điều chế rubi nhân tạo từ oxit nhơm.

Phản ứng xảy dùng xúc tác sợi amiang có chứa muội Pt. Ứng dụng làm pin nhiên liệu

2 2

2 2

2 ( ) 4 (dd)=4H ( ) 4

( ) 2 ( ) 4 4 (dd)

H k OH O l e

O k H O l e OH





 

  

-+

2 ( ) 2 ( ) 2 2 ( )

Department of Inorganic Chemistry - HUT

Ở nhiệt độ cao, hidro chiếm oxi nhiều hợp chất, đa số oxit kim loại

2 2

3 4 2 2

( ) ( ) ( ) ( )

( ) 4 ( ) ( ) 4 ( )

CuO r H k Cu r H O k

Fe O r H k Fe r H O k

  

  

Phản ứng dùng để định lượng hidro.

Phản ứng khử dùng để điều chế số kim loại Ni, Fe, W.

Khi có Pt làm xúc tác, hidro khử nhiều hợp chất hữu tan dung môi hữu như: khử hợp chất không no thành hợp chất no, khử andehit thành rượu.

Ở áp suất cao, hidro đẩy số kim loại khỏi dung dịch muối chúng.

HCl Zn

H2

H2

Department of Inorganic Chemistry - HUT

Hidro sinh

2 4 4

_ 2

4 2

( ) 2

5 3 4

Zn H SO loang ZnSO H

MnO H H  Mn  H O

  

   

Hidro sinh hidro nguyên tử hoạt tính hóa học mạnh

hơn phân tử:

-Trong phản ứng hóa học, H2 cần phân hủy thành nguyên tử 

tiêu thụ nhiều nhiệt.

-H phản ứng với chất tỏa nhiều nhiệt.

-Phản ứng phát < 436 kJ/mol H2 không tự xảy ra.

Ứng dụng làm đèn xì nguyên tử H để hàn cắt kim loại.

H + SO2 + H+  H 2S

H + NO2-, NO

3- + OH-  NH3

Synthesis and Production of Hydrogen:

Synthesis and Production of Hydrogen:

Commercial Production -

Commercial Production -

1 “Water Gas” Reaction

1 “Water Gas” Reaction

C (s) + H

C (s) + H22O (g)O (g) HH22 (g) (g) + CO (g) + CO (g)

This is an inexpensive process that produces “water

This is an inexpensive process that produces “water

gas which is an important industrial fuel source.

gas which is an important industrial fuel source.

H

H22 (g) + CO (g) + O (g) + CO (g) + O22 (g) (g) CO CO22 (g) + H (g) + H22O (g)O (g) + + thermalthermal

H

H22 is difficult to purify from the water gas mixture. is difficult to purify from the water gas mixture. However, it can be done using the following reaction:

However, it can be done using the following reaction:

H

H22 (g) + CO (g) (g) + CO (g) HH22O (g)O (g) 450

450ooCC

Fe

Fe22OO33

2

2 HH22 (g) (g) + CO + CO22 (g) (g)

H

H22 (g) + CO (g) + CO22 (g) + K (g) + K22COCO3 3 (aq) + H(aq) + H22O (l)O (l)

2 KHCO

2 Steam-Hydrocarbon Reforming

2 Steam-Hydrocarbon Reforming

A Natural gas or oil refinery feedstock

A Natural gas or oil refinery feedstock

desulfur-ization

ization

H

H22S (g) + NaOH (aq)S (g) + NaOH (aq) Na Na22S (aq) + HS (aq) + H22O (l)O (l) B Reforming

B Reforming

CH

CH44 (g) + H (g) + H22O (g)O (g) CO (g) + CO (g) + HH

2

2 (g) (g)

760

760

-980

980ooCC

600 psi

600 psi

Ni Cat.

CO (g) + H

CO (g) + H22O (g)O (g) COCO22 (g) + (g) + HH22 (g) (g)

CO (g) + H

CO (g) + H22 (g) (g) CHCH44 (g) + H (g) + H22O (g)O (g)

Two reversible reactions occur setting up an equilibrium

Two reversible reactions occur setting up an equilibrium

mixture of H

mixture of H2, 2, CO, COCO, CO22, and H, and H22O:O:

C High Temperature Shift Reaction

C High Temperature Shift Reaction

Exothermic

Exothermic

CO (g) + H

CO (g) + H22O (g)O (g) 350350 CO CO22 (g) + (g) + HH22 (g) (g)

o

oCC

Fe/Cu

Fe/Cu

Cat.

D Low Temperature Shift Reaction

D Low Temperature Shift Reaction

CO (g) + H

CO (g) + H22O (g)O (g) 200200 CO CO22 (g) + (g) + HH22 (g) (g)

o

oCC

Exothermic

Exothermic

This reduces CO content to about 0.2 % by volume.

This reduces CO content to about 0.2 % by volume.

E Methanation

E Methanation (For further removal of CO)(For further removal of CO)

CO (g) + H

CO (g) + H22 (g) (g) 350350 CH CH44 (g) + H (g) + H22O (g)O (g)

o

oCC

F CO

F CO22 Removal Removal 2 HOCH

2 HOCH22CHCH22NHNH2 2 + CO + CO22 + H + H22OO

G Pressure-Swing Absorption (PSA)

G Pressure-Swing Absorption (PSA)

Low temperature shift and methanation can both be

Low temperature shift and methanation can both be

replaced by this method which involves passing gas from

replaced by this method which involves passing gas from

high temperature shift reactor through molecular sieves to

high temperature shift reactor through molecular sieves to

produce hydrogen with

produce hydrogen with 99.9 % purity. 99.9 % purity.

K

K22COCO33 (aq) (aq) + CO + CO22 (g) + H (g) + H22O (l)O (l) 2 KHCO2 KHCO33 (aq) (aq)

The hydrocarbon-steam reforming process can also be

The hydrocarbon-steam reforming process can also be

done using the products of the “cracking” process in oil

done using the products of the “cracking” process in oil

refineries, e.g.,

3 Electrolysis of NaOH (aq) or KOH (aq)

3 Electrolysis of NaOH (aq) or KOH (aq)

Anode:

Anode: 2 OH2 OH HH

2

2O + 1/2 OO + 1/2 O22 + e + e-

-Cathode:

Cathode: 2 H2 H22O + eO + e 2 OH2 OH + + H H

2

2

2 H

2 H22OO 2 2 HH22 + O + O22

Ni anodes and Fe cathodes are used in this process This

Ni anodes and Fe cathodes are used in this process This

process is the most expensive method for producing H

4 Electrolysis of Brine -

4 Electrolysis of Brine - A By-product of the productionA By-product of the production

of chlorine in the chlor-alkali industry.

of chlorine in the chlor-alkali industry.

2 NaCl (aq) + H

2 NaCl (aq) + H22O (l)O (l) Cl Cl22 (g) + (g) + HH22 (g) (g) + NaOH (aq) + NaOH (aq)

Insufficient Hydrogen is found in the atmosphere

Insufficient Hydrogen is found in the atmosphere

There-fore, it must be produced from compounds containing it.

fore, it must be produced from compounds containing it.

1 Water as a Source for Hydrogen

1 Water as a Source for Hydrogen

Laboratory Synthesis

Laboratory Synthesis

-A At ordinary temperatures

A At ordinary temperatures

1) By highly electropositive metals

2 Na (s) + H

2 Na (s) + H22O (l)O (l) NaOH (aq) + NaOH (aq) + HH22 (g) (g) Ca (s) + H

Ca (s) + H22O (l)O (l) Ca(OH)Ca(OH)22 (s) + (s) + HH22 (g) (g) 2) By hydrides of electropositive metals

2) By hydrides of electropositive metals

LiH (s) + H

LiH (s) + H22O (l)O (l) LiOH (aq) + LiOH (aq) + HH22 (g) (g) CaH

CaH22 (s) + H (s) + H22O (l)O (l) Ca(OH)Ca(OH)22 (s) + (s) + HH22 (g) (g) 3) By electrolysis of acidified solution

3) By electrolysis of acidified solution

2 H

B At higher temperatures

B At higher temperatures

Mg (s) + H

Mg (s) + H22O (g)O (g) MgO (s) + MgO (s) + HH22 (g) (g) Zn (s) + H

Zn (s) + H22O (g)O (g) ZnO (s) + ZnO (s) + HH22 (g) (g) 3 Fe (s) + H

3 Fe (s) + H22O (g)O (g) FeFe33OO44 (s) + (s) + HH22 (g) (g)

All of these are Exothermic

All of these are Exothermic

CO (g) + H

CO (g) + H22O (g)O (g) COCO22 (g) + (g) + HH22 (g) (g)

C (s) + H

2 NonOxidizing Acids as a Source for Hydrogen

2 NonOxidizing Acids as a Source for Hydrogen

-Zn (s) + dil H

Zn (s) + dil H22SOSO44 (aq) (aq) ZnSOZnSO44 (aq) + (aq) + HH22 (g) (g)

Zn (s) + HCl (aq)

Zn (s) + HCl (aq) ZnCl ZnCl22 (aq) + (aq) + HH22 (g) (g)

Mg (s) + HCl (aq)

Mg (s) + HCl (aq) MgCl MgCl22 (aq) + (aq) + HH22 (g) (g)

Oxidizing acids DON’T WORK!!

Oxidizing acids DON’T WORK!!

Zn (s) + HNO

Zn (s) + HNO3 3 (aq)(aq) Zn(NO Zn(NO33))22 (aq) + NO (aq) + NO22

+ H+ H22O (l)O (l)

Assignment:

3 Bases as a Source for Hydrogen

3 Bases as a Source for Hydrogen

-Zn (s) + NaOH (aq) + H

Zn (s) + NaOH (aq) + H22O (l)O (l) NaNa22[Zn(OH)[Zn(OH)44]]

++ HH22 (g) (g) Al (s) + KOH (aq) + H

Al (s) + KOH (aq) + H22O (l)O (l) KK22[Al(OH)[Al(OH)44]]

Department of Inorganic Chemistry - HUT

Biological routes to H2

H2 is produced by several microorganisms, usually via

reactions catalyzed by enzymes called hydrogenases These iron and sometimes nickel-containing catalysts

transfer reducing equivalents produced during

fermentation to water Some of these organisms will

split water, via operation of O2- and H2-generating cycles

which operate in the light and in the dark respectively.

Other rarer but mechanistically interesting routes to H2

production also exist in nature Nitrogenase produces approximately one equivalent of H2 for each equivalent of

N2 reduced to ammonia Some phosphatases reduced

Department of Inorganic Chemistry - HUT

Hidrua nguyên tố: hợp chất hidro với nguyên tố

Hidrua ion

Hidrua ion

Hidrua kiểu kim loại

Hidrua kiểu kim loại

Hidrua cộng hóa trị

Department of Inorganic Chemistry - HUT

Hidrua ion:

- Là tinh thể không màu, giống với muối  gọi hidrua muối Hidro có

lực với e bé  xu hướng tạo ion âm yếu so với halogen.

- Do tính thu nhiệt ion H-  kim loại hoạt động mạnh kim loại

kiềm kiềm thổ tạo hidrua ion Bản chất ion thể rõ tính nóng chảy nhiệt độ cao dẫn điện nóng chảy.

- Chế tạo cách đun nóng kim loại khí hidro.

218 / 113 /

2

66 / 326 /

152 / 213 /

2 1 1 ( ) ( ) ( ) ( ) 2 2 ( ) ( ) ( ) ( ) 1 1 ( ) ( ) ( ) ( ) 2 2 o o o o o o

H kJ mol H kJ mol

H kJ mol H kJ mol

H kJ mol H kJ mol

H k H k Br k Br k

H k e H k Br k e Br k

H k e H k Br k e Br k

                          2 2 2 2 2 o o t t

Na H NaH Ca H CaH

   

Hidrua ion

Department of Inorganic Chemistry - HUT

Hidrua ion:

-Về mặt hóa học, hidrua ion có hoạt tính cao  phản ứng nhanh hồn tồn

với chất cho dù vết ion H+ để giải phóng khí hidro.

- Làm chất khử tổng hợp hữu cơ, LiH, NaH - Coi hidrua ion muối axit yếu H-H.

2 2

2 2 2 ( )2 2 2

NaH H O NaOH H

CaH H O Ca OH H

  

  

/

2 2.25

2 2 2

o

H H V

H e H

  



 

Department of Inorganic Chemistry - HUT

-Là hidrua phi kim số kim loại lưỡng tính.

-Hóa học hidrua cộng hóa trị phụ thuộc mạnh vào chất nguyên tố liên kết với H.

-Liên kết H-X nhóm giảm từ xuống; chu kỳ nói chung tăng từ trái sang phải Nguyên nhân phụ thuộc vào độ âm điện kích thước nguyên tử nguyên tố X

-Có nhiệt độ nóng chảy nhiệt độ sôi thấp Uvdv không cao HF, H2O, NH3 có nhiệt độ nóng chảy sơi cao bất thường có thêm liên kết hidro.

-Độ hòa tan nước phụ thuộc vào độ phân cực phân tử, kích thước phân tử và có mặt liên kết hidro HF tan nước theo tỷ lệ HCl, HBr, HI, NH3 tan nhiều nước; hidrua cộng hóa trị cịn lại tan khơng tan nước.

-Một số hidrua có tính axit HX, H2X; số có tính bazơ XH3

Hidrua cộng hóa trị

Department of Inorganic Chemistry - HUT

-Nhiều kim loại chuyển tiếp hấp thụ hidro tạo thành chất rắn có thành phần xác định UH3, VH, ScH2, không xác định PdHx.

-So với kim loại ban đầu, hidrua kim loại có khả phản ứng với oxi nước, dòn hơn, chất dẫn điện bán dẫn, bề giống kim loại.

-Đã có nhiều nghiên cứu hidrua kim loại cấu tạo phức tạp nên chưa hiểu hết loại hợp chất này.

-Có tính chất từ lý thú.

-Khi hấp thụ giải phóng hidro gây biến đổi thể tích  có số ứng

dụng tạo kim loại bột.

Hidrua kiểu kim loại

Department of Inorganic Chemistry - HUT

CHƯƠNG II

HYDRO VÀ NƯỚC

Nước

Tính chất lý học Tính chất hóa học

Trạng thái thiên nhiên phương pháp tinh chế Sự gây ô nhiễm môi trường nước

Xử lý nước thải Hidro peoxit

You are 65% water

H2O molecule

sp3

O-H = 0.9584 Å μ = 1.84 D

Bắt đầu phân hủy 1000 oC

Phân hủy % 2000 oC

2 2 2 2

s z x y

Hydrogen bonding

• Polarity means small negative charge at O end

• Small positive charge at H end

• Attraction between + and – ends of water

molecules to each other or other ions

• Molecules ‘order’

Hydrogen bonding

• Hydrogen bonds are weaker than covalent bonds but still strong enough to result in

–Solid, liquid, gas at Earth’s

surface

–Unusual thermal properties

Hydrogen bonding • Hydrogen bonds are

weaker than covalent bonds but still strong enough to result in

– High surface tension (water beads)

– High solubility of chemical compounds in water

• Water is especially good at dissolving ionic

compounds (salts)

Hydrogen-Bonding

Maximum Density 40C

•Ice is less dense than water

Density of Water

11.3

( )

0

nc L R nc

nc nc

VT V V T

dT

dP H H

 

  

Density of water

• Density of water increases as

temperature decreases to 4oC

• Density of ice is less than density of water

• From 4oC to 0oC density of water

Changes of state due to adding or subtracting heat

• Heat is energy of moving molecules • Calorie is amount of heat needed to

raise the temperature of gram of water

by 1o C

• Temperature is measurement of average kinetic energy

Unusual thermal properties of H2O

• H2O has high boiling point • H2O has high freezing point

– If water did not have hydrogen bonds, ice would melt at -90ºC and water would

boil at -68ºC

Unusual thermal properties of H2O

• High latent (hidden) heats of

– Vaporization/condensation – Melting/freezing

– Evaporation

Unusual thermal properties of H2O

• Water high heat capacity

– Amount of heat required to raise the

temperature of gram of any substance 1o C

– Water can take in/lose lots of heat without changing temperature

– Rocks low heat capacity

• Rocks quickly change temperature as they gain/lose heat

That’s why beach-sand is cold on an August nightThat’s why beach-sand is cold on an August night

• Water has unusually high specific heats.

– ice: 2.03 J/g.oC or 36.6 J/mol.oC

– liquid: 4.186 J/g.oC or 75.4 J/mol.oC

– steam: 1.99 J/g.oC or 35.9 J/mol.oC

• Water has unusually high latent heats.

– fusion: 333 J/g or 6.01 kJ/mol – vaporization: 2.44 kJ/g or 44.0 kJ/mol

Water molecules in different states of matter

What are the condensation and vaporization points for pure water?

Desalination processes • Remove salt from seawater

• Distillation most common process

• Electrolysis – (not just for hair removal!)

• Reverse osmosis (you’ve all drank ‘RO’ water before)

Reverse Osmosis Water (‘RO’ water)

Commercial water Supply plants

pH of Water

pH is a measure of the H+ concentration in water

pH = -log[H+]

dissociation of water H2O H+ + OH

-for pure water, pH = 7.0 [H+] = 10-7 M

but other solutes may add or remove H+ ions

Department of Inorganic Chemistry - HUT

Nước vừa có tính oxi hóa (do hidro có số oxi hóa +1) vừa có tính khử (do oxi có số oxi hóa -2)

Ở điều kiện thường, tính chất thể yếu nên:

 chất khử mạnh kim loại kiềm, kiềm thổ  chất oxi hóa mạnh F

mới dễ dàng phản ứng với nước.

2

2 2 2

2 2 2

2 2 4

Na HOH NaOH H

F H O HF O

   

Department of Inorganic Chemistry - HUT

Về mặt nhiệt động, khả xảy phản ứng oxi hóa - khử sau:

2

2

2

2 / /

0.059 2 2 ( ) lg

2

o

H H H H

H

H H e H k

p              

2 2 2

4

2 / /

0.059

( ) 4 4 2 ( ) lg

4

o

O H O O H O O

O k  e  H   H O l    p H 

2 2 2 / / 1 7 0.00 1.23 H O o H H o

O H O

p p atm

pH V V       

 /

0.413

H H V

  

2 / 0.817

O H O V

 

Nước bị OXH

Nước bị KH

Không bị OXH - KH

Department of Inorganic Chemistry - HUT

Oxidant Oxidation Potential, V

Fluorine 3.0

Hydroxyl radical 2.8

Ozone 2.1

Hydrogen peroxide 1.8 Potassium permanganate 1.7 Chlorine dioxide 1.5

Department of Inorganic Chemistry - HUT Chemical properties

98.74 /

2 2 -119.2 kJ/mol 2 2

2 oo 2

H kJ mol

G

H O   H O O

 

       

It usually acts as an oxidizing agent, but there are many

reactions where it acts as a reducing agent, releasing

oxygen as a by-product

It also readily forms both inorganic and organic

The rate of decomposition is dependent on the temperature and concentration of the peroxide, as well as the pH and the presence of impurities and stabilizers

Hydrogen peroxide is incompatible with many substances that catalyse its decomposition, including most of the transition metals and their compounds

Common catalysts include manganese dioxide, potassium permanganate, and silver The same reaction is catalysed by the enzyme catalase, found in the liver, whose main function in the body is the removal of toxic byproducts of metabolism and the reduction of oxidative stress The decomposition occurs more rapidly in alkali, so acid is often added as a stabilizer.

Spilling high concentration peroxide on a flammable substance can cause an immediate fire fueled by the oxygen released by the decomposing hydrogen peroxide High-strength peroxide (also called high-test peroxide, or HTP) must be stored in a vented container to prevent the buildup of oxygen gas, which would otherwise lead to the eventual rupture of the container Any container must be made of a compatible material such as PTFE, polyethylene, stainless steel or aluminium and undergo a cleaning process (passivation) to remove all contamination prior to the introduction of peroxide (Note that while compatible at room temperature, polyethylene can explode with peroxide in a fire.)

Department of Inorganic Chemistry - HUT

Redox reactions

Redox reactions

In aqueous solution, hydrogen peroxide can oxidize or reduce a variety of inorganic ions When it acts as a reducing agent, oxygen gas is also produced In acid solution Fe2+ is oxidized to Fe3+,

2 Fe2+(aq) + H2O2 + H+(aq) → Fe3+(aq) + 2H2O(l)

and sulfite (SO32−) is oxidized to sulfate (SO42−) However, potassium permanganate is reduced to Mn2+ by acidic H2O2 Under alkaline conditions, however, some of these reactions reverse; Mn2+ is oxidized to Mn4+ (as

MnO2), yet Fe3+ is reduced to Fe2+

2 Fe3+ + H2O2 + OH− → Fe2+ + H2O + O2

Hydrogen peroxide is frequently used as an oxidising agent in organic chemistry One application is for the oxidation of thioethers to sulfoxides.[citation needed] For example, methyl phenyl sulfide was oxidised to methyl phenyl sulfoxide in 99% yield in methanol in 18 hours (or 20 minutes using a TiCl3 catalyst):

Ph-S-CH3 + H2O2 → Ph-S(O)-CH3 + H2O

Department of Inorganic Chemistry - HUT

Formation of peroxide compounds

Formation of peroxide compounds

Hydrogen peroxide is a weak acid, and it can form hydroperoxide or peroxide salts or derivatives of many metals For example, with aqueous solutions of

chromic acid (CrO3), it can form an unstable blue peroxide CrO(O2)2 It can also produce peroxoanions by reaction with anions; for example, reaction with borax

leads to sodium perborate, a bleach used in laundry detergents: Na2B4O7 + H2O2 + NaOH → Na2B2O4(OH)4 + H2O

H2O2 converts carboxylic acids (RCOOH) into peroxy acids (RCOOOH), which are themselves used as oxidizing agents Hydrogen peroxide reacts with acetone

to form acetone peroxide, and it interacts with ozone to form hydrogen trioxide Reaction with urea produces carbamide peroxide, used for whitening teeth An acid-base adduct with triphenylphosphine oxide is a useful "carrier" for H2O2 in

some reactions

Hydrogen peroxide reacts with ozone to form trioxidane [edit]

Alkalinity

Alkalinity

Hydrogen peroxide is a much weaker base than water, but it can still form adducts with very strong acids The superacid HF/SbF5 forms unstable

Department of Inorganic Chemistry - HUT Manufacture

Hydrogen peroxide is manufactured today almost exclusively by the autoxidation of 2-ethyl-9,10-dihydroxyanthracene to 2-ethylanthraquinone and hydrogen peroxide using oxygen from the air The

anthraquinone derivative is then extracted out and reduced back to the dihydroxy compound using hydrogen

gas in the presence of a metal catalyst The overall equation for the process is deceptively simple: H2 + O2 → H2O2

However the economics of the process depend on effective recycling of the quinone and extraction solvents, and of the hydrogenation catalyst

Formerly inorganic processes were used, employing the electrolysis of an aqueous solution of sulfuric acid or acidic ammonium bisulfate (NH4HSO4), followed by hydrolysis of the peroxydisulfate ((SO4)2)2− which is

formed

In 1994, world production of H2O2 was around 1.9 million tonnes, most of which was at a concentration of 70% or less In that year bulk 30% H2O2 sold for around US $0.54 per kg, equivalent to US $1.50 per kg

(US $0.68 per lb) on a "100% basis" [edit]

Concentration

Hydrogen peroxide works best as a propellant in extremely high concentrations However, there are very few suppliers of high-purity hydrogen peroxide, and they are averse to selling to any but the largest institutions As a result, amateurs wishing to use this for rocket fuel usually have to purchase 70% or lower-purity (most

of the remaining 30% is water, and sometimes there are traces of stabilizing materials, such as tin), and increase its concentration themselves Many try distillation, but this is extremely dangerous with hydrogen

peroxide; peroxide vapour can detonate at a temperature of about 70 °C (158 °F) A safer approach is sparging, possibly followed by fractional freezing, but, even when using this method, contaminants may still

often cause explosions

In the 1950s, high-test peroxide was more readily available, but because of safety concerns bulk manufacturers have since switched over to handling lower concentrations of H2O2 whenever possible Some amateur groups have expressed interest in manufacturing their own peroxide, for their use and for

-Ái lực e H stable w h neutrons trace 2 y β− 3He Discovered by: Phase gas Density Melting point 32.97 K 252.87 °C °F Boiling point Triple point Critical point Heat of fusion ) 0.117 kJ·mol Heat of vaporization Heat capacity laboratory, acids zinc Aluminum he electrolysis cathode enzymes hydrogenases iron nickel catalysts fermentation split water, Nitrogenase phosphite to H Tính chất lý họcTính chất hóa học oxidizing agent peroxides pH nces that catalyse transition metals manganese dioxide, potassium permanganate, d silver catalase, f liver, metabolism oxidative stress alkali, compatible PTFE polyethylene, stainless steel aluminium passivation hydroxyl Fenton's reagent. oxygen H+ sulfite sulfate alkaline MnO2) OH− thioethers sulfoxides [citation needed methyl phenyl TiCl3 epoxidation acrylic acids alkylboranes alcohols, hydroboration-oxidation hydroperoxide salts chromic acid anions; borax o sodium perborate carboxylic acids acetone acetone peroxide ozone hydrogen trioxide urea carbamide peroxide, h triphenylphosphine oxide trioxidane [edit base superacid HF/ SbF5 autoxidation anthraquinone extracted hydrogen