Hydro and Water.pdf

Department of Inorganic Chemistry - HUT

CHƯƠNG IIHYDRO VÀ NƯỚC

Hidro

Cấu tạo nguyên tử

Tính chất lý học

Tính chất hóa học

Trạng thái thiên nhiên và phương pháp điều chế

Hidrua của các nguyên tố

Hidrua ion

Hidrua cộng hóa trị

Hidrua kiểu kim loại

Nước



Trạng thái thiên nhiên và phương pháp tinh chế

Sự gây ô nhiễm môi trường nước

Xử lý nước thải

Hidro peoxit

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 về khả năng mất e thành cation nhưng khác ở:

-Năng lượng ion hóa lớn gấp vài ba lần so với kim loại kiềm.

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

nhiễu loạn đám mây e của các nguyên tử xung quanh.

-Proton không thể tồn tại một mình mà luôn kết hợp với nguyên tử hay phân tử khác, H3O+

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

-Ái lực e của H bằng gần 1/5 so với ái lực e của halogen.

-Ion H- có cấu trúc e của He (1s2)

-Ion H- tự do có khả năng tồn tại trong hidrua muối như KH, CaH2

àH có vị trí đặc biệt trong bảng hệ thống tuần hoàn các nguyên tố hóa họcàH vừa giống-khác với các kim loại kiềm và halogenàH có đặc điểm mà những nguyên tố khác không có (do bản chất của proton và không có e chắn điện tích hạt nhân) như tạo liên kết hidro, cầu hidro và hợp chất không hợp thức với kim loại)

Occurrence and Abundance:Occurrence and Abundance:Elemental Composition of the Sun & the UniverseElemental Composition of the Sun & the Universe

SunSun UniverseUniverse

HydrogenHydrogen 92.5 %92.5 % 90.87 %90.87 %HeliumHelium 7.3 %7.3 % 9.08 %9.08 %All Others All Others 0.2 %0.2 % 0.05 %0.05 %

Elemental Composition of the EarthElemental Composition of the Earth’’s Crust (ppm mass)s Crust (ppm mass)O O -- 455 000 455 000 Mg Mg -- 27 64027 640Si Si -- 272 000272 000 Na Na -- 22 70022 700Al Al -- 83 00083 000 K K -- 18 40018 400Fe Fe -- 62 00062 000 Ti Ti -- 63206320Ca Ca -- 46 600 46 600 H H -- 15201520

Elemental Composition of the Human Body:Elemental Composition of the Human Body:

By AtomsBy Atoms By MassBy MassH H -- 63.0 %63.0 % 10.0 %10.0 %O O -- 25.5 %25.5 % 64.6 %64.6 %C C -- 9.5 %9.5 % 18.0 %18.0 %N N -- 1.4 %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.more compounds than any other element.

HH22

--CC--CC--

MHMHxx

HXHXHH22OO

--CC--CC--

--CC--OHOH

M + HM + H22OO

NHNH33

N2M

X2

O2

MxOy

C=

O

C=C

C=C

1671 1671 -- Robert Boyle 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 1766 -- Henry Cavendish 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 1781 -- Henry Cavendish 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 1783 -- Antoine Lavoisier Antoine Lavoisier -- Proposed the name Proposed the name

““hydrogenhydrogen”” from the Greek for from the Greek for ““water formerwater former””..


Main article: Isotopes of hydrogen

iso NA half-life DM DE (MeV) DP

1H 99.985% H is stable with 0 neutrons

2H 0.0115% H is stable with 1 neutrons

3H trace 12.32 y β− 0.019 3HeHistorical information

Discovered by: Henry Cavendish (1731-1810)

Discovered at: London, England

Discovered when: 1766

Origin of name: From the Greek words "hydro" and "genes" meaning "water" and "generator"

Molecular Properties of Hydrogen:Molecular Properties of Hydrogen:

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

H, HH, H22 HH++, H, H--, H, H22++, H, H33

++, D, D, D, D22, D, D++, D, D--,,

HD, HT, DT, T, THD, 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++ + 1 n+ 1 n00

C. C. TTritium ritium -- 33HH 1 P1 P++ + 2 n+ 2 n00

(99.986 %)(99.986 %)

(0.014 %)(0.014 %)

(7 x 10(7 x 10--1616 %)%)

Physical Properties:Physical Properties: HH22 DD22 TT22

Atomic Mass, uAtomic Mass, u 1.00781.0078 2.0141 3.01602.0141 3.0160

Freezing Point, Freezing Point, ooCC --259.0259.0 --254.3 254.3 --252.4252.4

Boiling Point, Boiling Point, ooCC --252.6252.6 --249.3 249.3 --248.0248.0

Bond Length, pmBond Length, pm 74.1474.14 74.14 (74.14)74.14 (74.14)

∆∆HHDissociationDissociation, kJ/mol 435.9, kJ/mol 435.9 443.4 446.9443.4 446.9

∆∆HHFusionFusion, kJ/mol, kJ/mol 0.1170.117 0.197 0.2500.197 0.250

∆∆HHVaporizationVaporization, kJ/mol 0.904, kJ/mol 0.904 1.226 1.3931.226 1.393

Vapor Pressure, torr 54 5.8 Vapor Pressure, torr 54 5.8 --


Hidro Physical properties

Phase gas

Density(0 °C, 101.325 kPa)

0.08988 g/L

Melting point14.01 K

(−259.14 °C, −434.45 °F)

Boiling point20.28 K

(−252.87 °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) (H

2)

28.836 J·mol−1·K−1

Electronic Structure and Modes of Reaction:Electronic Structure and Modes of Reaction:

Hydrogen has the simplest electronic structure of allHydrogen has the simplest electronic structure of allelements. It consists of a nucleus containing one protonelements. It consists of a nucleus containing one protonand one electron in the 1s orbital.and one electron in the 1s orbital.

1s1 electron

+

Modes of Reactivity:Modes of Reactivity:1. By losing an electron to form a hydrogen ion, H1. By losing an electron to form a hydrogen ion, H++..

Protons are extremely smallProtons are extremely smalland, therefore, are and, therefore, are VERYVERYpolarizing because they have apolarizing because they have avery large very large charge densitycharge density..They associate strongly withThey associate strongly withmolecules around them. Thus,molecules around them. Thus,in water or in acids they formin water or in acids they formthe the hydronium ion, Hhydronium ion, H33OO++..

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 ioniccrystalline solids of some of the Groups 1crystalline solids of some of the Groups 1and 2 metal hydrides. Only the most and 2 metal hydrides. Only the most elecelec--tropositivetropositive metals will react to form ionicmetals will react to form ionic((salinesaline) hydrides.) hydrides.

3. By forming an electron pair (covalent) bond with3. By forming an electron pair (covalent) bond withanother atom.another atom.

..

H • • Cl :..

..H • • Cl :..

....H : Cl :H : Cl :

....NonNon--metals and somemetals and somemetals form covalentmetals form covalenthydrides.hydrides.


Trạng thái thiên nhiên và 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 + 2 H+ → Zn2+ + H2

Aluminum produces H2 upon treatment with acids but also with base:

2 Al + 6 H2O → 2 Al(OH)3 + 3 H2

The electrolysis of water is a simple but expensive method of producing

hydrogen. Typically the cathode electrode is made from platinum.



Tính bền nhiệt

Tính khử

Tính oxy hóa

20002 ( ) 2KH k H→ 298 432 /oH kJ mol∆ =

H2 với vỏ e của He nên rất bền nhiệt, khó phân hủy thành H

Ở p = 1 atm và 2000 K, H2 phân hủy 0.1 %.

Ở 5000 K phân hủy đạt 95 %

Quá trình phân hủy phải thu nhiều nhiệt.

à Ở nhiệt độ thường hidro kém hoạt động về mặt hóa học.

H – e = H+ ΔHo = 1312 kJ/mol

2 2( ) ( ) 2 ( )H k F k HF k+ =

5502 2 22 ( ) ( ) 2 ( )

241 /

o C

o

H k O k H O k

H kJ mol

+ →

∆ = −

Phản ứng xảy ra ở nhiệt độ thường, không cần xúc tác.

Hỗn hợp cùng thể tích hidro và flo nổ ngay ở nhiệt độ thấp

Hỗn hợp này không phản ứng ở nhiệt độ thấp nhưng lại nổ khi có ngọn lửa.

Khí hidro cháy êm dịu trong oxi tinh khiết à phản ứng tỏa ra nhiều nhiệt, ngọn lửa

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

Pt, điều chế rubi nhân tạo từ oxit nhôm.

Phản ứng có thể xảy ra khi dùng xúc tác là sợi amiang có chứa muội Pt.

Ứng dụng làm pin nhiên liệu

Tính khử

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 ( )H k O k H O l+ =


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

2 2

3 4 2 2

( ) ( ) ( ) ( )

( ) 4 ( ) 3 ( ) 4 ( )

CuO r H k Cu r H O k

Fe O r H k Fe r H O k

+ = +

+ = +

Phản ứng 1 có thể dùng để định lượng hidro.

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

Khi có Pt làm xúc tác, hidro có thể khử nhiều hợp chất hữu cơ tan trong các dung

môi hữu cơ như: khử hợp chất không no thành hợp chất no, khử andehit thành

rượu.

Ở áp suất cao, hidro có thể đẩy một số kim loại ra khỏi dung dịch muối của chúng.

HCl

Zn

H2

H2

CuO

Department of Inorganic Chemistry - HUTHidro mới sinh

2 4 4

_ 24 2

( ) 2

5 3 4

Zn H SO loang ZnSO H

MnO H H Mn H O+ +

+ = +

+ + = +

Hidro mới sinh là hidro nguyên tử àhoạt tính hóa học mạnh

hơn phân tử:

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

tiêu thụ nhiều nhiệt.

-H phản ứng với các chất tỏa ra nhiều nhiệt.

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

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

H + SO2 + H+à H2S

H + NO2-, NO3

- + OH-à NH3

Các phản ứng trên không xảy ra với hidro nguyên tử.

Synthesis and Production of Hydrogen:Synthesis and Production of Hydrogen:

Commercial Production Commercial Production --

1. 1. ““Water GasWater Gas”” ReactionReaction

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

This is an inexpensive process that produces This is an inexpensive process that produces ““waterwatergas which is an important industrial fuel source.gas which is an important industrial fuel source.

HH22 (g) + CO (g) + O(g) + CO (g) + O22 (g)(g) COCO22 (g) + H(g) + H22O (g)O (g) + + thermalthermalenergyenergy

HH22 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:

HH22 (g) + CO (g)(g) + CO (g)HH22O (g)O (g)

450450ooCCFeFe22OO33

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

HH22 (g) + CO(g) + CO22 (g) + K(g) + K22COCO3 3 (aq) + H(aq) + H22O (l)O (l)

2 KHCO2 KHCO33 (aq) + (aq) + HH22 (g)(g)

2. Steam2. Steam--Hydrocarbon ReformingHydrocarbon Reforming

A. Natural gas or oil refinery feedstock desulfurA. Natural gas or oil refinery feedstock desulfur--izationization

HH22S (g) + 2 NaOH (aq)S (g) + 2 NaOH (aq) NaNa22S (aq) + HS (aq) + H22O (l)O (l)

B. ReformingB. Reforming

CHCH44 (g) + H(g) + H22O (g)O (g) CO (g) + 3 CO (g) + 3 HH22 (g)(g)

760 760 --980980ooCC600 psi600 psiNi Cat.Ni Cat. EndothermicEndothermic

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

CO (g) + 3 HCO (g) + 3 H22 (g)(g) CHCH44 (g) + H(g) + H22O (g)O (g)

Two reversible reactions occur setting up an equilibriumTwo reversible reactions occur setting up an equilibriummixture of Hmixture of H2, 2, CO, COCO, CO22, and H, and H22O:O:

C. High Temperature Shift ReactionC. High Temperature Shift Reaction

ExothermicExothermic

CO (g) + HCO (g) + H22O (g)O (g) COCO22 (g) + (g) + HH22 (g)(g)350350ooCC

Fe/CuFe/CuCat.Cat.

D. Low Temperature Shift ReactionD. Low Temperature Shift Reaction

CO (g) + HCO (g) + H22O (g)O (g) COCO22 (g) + (g) + HH22 (g)(g)200200ooCC

ExothermicExothermic

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) + HCO (g) + H22 (g)(g) CHCH44 (g) + H(g) + H22O (g)O (g)350350ooCC

F. COF. CO22 RemovalRemoval2 HOCH2 HOCH22CHCH22NHNH2 2 + CO+ CO22 + H+ H22OO

(HOCH(HOCH22CHCH22NHNH3 3 ))22COCO33

G. PressureG. Pressure--Swing Absorption (PSA)Swing Absorption (PSA)

Low temperature shift and methanation can both beLow temperature shift and methanation can both bereplaced by this method which involves passing gas fromreplaced by this method which involves passing gas fromhigh temperature shift reactor through molecular sieves tohigh temperature shift reactor through molecular sieves to

produce hydrogen withproduce hydrogen with≥≥ 99.9 % purity.99.9 % purity.

KK22COCO33 (aq)(aq) + CO+ CO22 (g) + H(g) + H22O (l)O (l) 2 KHCO2 KHCO33 (aq)(aq)

The hydrocarbonThe hydrocarbon--steam reforming process can also besteam reforming process can also bedone using the products of the done using the products of the ““crackingcracking”” process in oilprocess in oilrefineries, e.g., refineries, e.g., CC33HH88 (g) + H(g) + H22O (g)O (g)

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

Anode:Anode: 2 OH2 OH-- HH22O + 1/2 OO + 1/2 O22 + 2 e+ 2 e--

Cathode:Cathode: 2 H2 H22O + 2 eO + 2 e-- 2 OH2 OH-- + + HH22

2 H2 H22OO 2 2 HH22 + O+ O22

Ni anodes and Fe cathodes are used in this process. ThisNi anodes and Fe cathodes are used in this process. Thisprocess is the most expensive method for producing Hprocess is the most expensive method for producing H22..

4. Electrolysis of Brine 4. Electrolysis of Brine -- A ByA By--product of the productionproduct of the productionof chlorine in the chlorof chlorine in the chlor--alkali industry.alkali industry.

2 NaCl (aq) + 2 H2 NaCl (aq) + 2 H22O (l)O (l) ClCl22 (g) + (g) + HH22 (g)(g) + NaOH (aq)+ NaOH (aq)

Insufficient Hydrogen is found in the atmosphere. ThereInsufficient 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 temperaturesA. At ordinary temperatures

1) By highly electropositive metals1) By highly electropositive metals

2 Na (s) + 2 H2 Na (s) + 2 H22O (l)O (l) NaOH (aq) + NaOH (aq) + HH22 (g)(g)

Ca (s) + 2 HCa (s) + 2 H22O (l)O (l) Ca(OH)Ca(OH)22 (s) + (s) + HH22 (g)(g)

2) By hydrides of electropositive metals2) By hydrides of electropositive metals

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

CaHCaH22 (s) + 2 H(s) + 2 H22O (l)O (l) Ca(OH)Ca(OH)22 (s) + 2 (s) + 2 HH22 (g)(g)

3) By electrolysis of acidified solution3) By electrolysis of acidified solution

2 H2 H22O (l)O (l) 2 2 HH22 (g)(g) + O+ O22 (g)(g)

B. At higher temperaturesB. At higher temperatures

Mg (s) + HMg (s) + H22O (g)O (g) MgO (s) + MgO (s) + HH22 (g)(g)

Zn (s) + HZn (s) + H22O (g)O (g) ZnO (s) + ZnO (s) + HH22 (g)(g)

3 Fe (s) + 4 H3 Fe (s) + 4 H22O (g)O (g) FeFe33OO44 (s) + (s) + HH22 (g)(g)

All of these are ExothermicAll of these are Exothermic

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

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

2. Non2. Non--Oxidizing Acids as a Source for Hydrogen Oxidizing Acids as a Source for Hydrogen --

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

Zn (s) + 2 HCl (aq)Zn (s) + 2 HCl (aq) ZnClZnCl22 (aq) + (aq) + HH22 (g)(g)

Mg (s) + 2 HCl (aq)Mg (s) + 2 HCl (aq) MgClMgCl22 (aq) + (aq) + HH22 (g)(g)

Oxidizing acids DONOxidizing acids DON’’T WORK!!T WORK!!

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

+ H+ H22O (l)O (l)

Assignment:Assignment: Balance this equation!Balance this equation!

3. Bases as a Source for Hydrogen 3. Bases as a Source for Hydrogen --

Zn (s) + 2 NaOH (aq) + 2 HZn (s) + 2 NaOH (aq) + 2 H22O (l)O (l) NaNa22[Zn(OH)[Zn(OH)44]]++ HH22 (g)(g)

Al (s) + 2 KOH (aq) + 2 HAl (s) + 2 KOH (aq) + 2 H22O (l)O (l) KK22[Al(OH)[Al(OH)44]]++ HH22 (g)(g)


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

phosphite to H2.


Hidrua của các nguyên tố: là hợp chất của hidro với các nguyên tố

Hidrua ionHidrua ion

Hidrua kiHidrua kiểểu kim lou kim loạạii

Hidrua cHidrua cộộng hng hóóa tra trịị


Hidrua ion:

- Là những tinh thể không màu, giống với muối à gọi là hidrua muối. Hidro có ái

lực với e rất béà xu hướng tạo ion âm rất yếu so với halogen.

- Do tính thu nhiệt của ion H- à chỉ những kim loại hoạt động mạnh như kim loại

kiềm và kiềm thổ mới tạo được hidrua ion. Bản chất ion được thể hiện rõ ở tính

nóng chảy ở nhiệt độ cao và dẫn điện khi nóng chảy.

- Chế tạo bằng cách đun nóng kim loại trong khí quyển hidro.

218 / 113 /

2 2

66 / 326 /

152 / 213 /

2 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 2o

o

t

t

Na H NaH

Ca H CaH

+ =

+ =Hidrua ionHidrua ion


Hidrua ion:

-Về mặt hóa học, hidrua ion có hoạt tính rất cao à phản ứng nhanh và hoàn toàn

với những chất có thể cho dù chỉ là những vết ion H+ để giải phóng khí hidro.

- Làm chất khử trong tổng hợp hữu cơ, LiH, NaH.

- Coi hidrua ion là muối của axit hết sức yếu là H-H.

2 2

2 2 2 22 ( ) 2

NaH H O NaOH H

CaH H O Ca OH H

+ = +

+ = +

/22.25

2 2 2

o

H HV

H e H

ε − =−

−+ =

Dùng CaH2 để điều chế nhanh hidro trong quân sự, để định lượng nước trong

các hợp chất hữu cơ


-Là hidrua của các phi kim và một số kim loại lưỡng tính.

-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 đi từ trái sang phải. Nguyên nhân phụ thuộc vào độ âm điện và

kích thước nguyên tử của nguyên tố X.

-Có nhiệt độ nóng chảy và nhiệt độ sôi thấp do Uvdv không cao. HF, H2O, NH3 có

nhiệt độ nóng chảy và sôi cao bất thường là do có thêm liên kết hidro.

-Độ hòa tan trong nước phụ thuộc vào độ phân cực phân tử, kích thước phân tử

và sự có mặt của liên kết hidro. HF tan trong nước theo bất kỳ tỷ lệ nào. HCl,

HBr, HI, NH3 tan nhiều trong nước; các hidrua cộng hóa trị còn lại thì ít tan hoặc

không tan trong nước.

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

Hidrua cHidrua cộộng hng hóóa tra trịị


-Nhiều kim loại chuyển tiếp hấp thụ hidro tạo thành chất rắn có thành phần

xác định như UH3, VH, ScH2, hoặc không xác định như PdHx.

-So với kim loại ban đầu, hidrua kim loại có khả năng phản ứng kém hơn

với oxi và nước, dòn hơn, là chất dẫn điện hoặc bán dẫn, bề ngoài giống

kim loại.

-Đã có nhiều nghiên cứu về hidrua kim loại nhưng do cấu tạo phức tạp nên

chưa hiểu hết về loại hợp chất này.

-Có tính chất từ lý thú.

-Khi hấp thụ và giải phóng hidro gây biến đổi thể tích à có một số ứng

dụng tạo kim loại bột.

Hidrua kiHidrua kiểểu kim lou kim loạạii


CHƯƠNG IIHYDRO VÀ NƯỚC

Nước



Trạng thái thiên nhiên và phương pháp tinh chế

Sự gây ô nhiễm môi trường nước

Xử lý nước thải

Hidro peoxit

You are 65% water

There are more water molecules in a single droplet of water than there are grains ofsand on Wrightsville Beach

H2O molecule

sp3

O-H = 0.9584 Å

μ = 1.84 D

Bắt đầu phân hủy 1000 oC

Phân hủy 2 % ở 2000 oC

2 2 2 2s z x yσ σ π π=

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’themselves with these relatively weak H-bonds

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

–Unusual density

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)

• This is why the ocean is ‘salty’

Hydrogen-Bonding and the Unusual Properties of Water

Maximum Density40C

•Ice is less dense than water

Density of Water

11.3

( )0nc L R nc

nc nc

VT V V TdT

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 decreases as temperature decreases

Density of water, the reason why ice floats

Effect of Hydrogen-Bonding on Boiling Point

Phase Diagram 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 1 gram of water by 1o C

• Temperature is measurement of average kinetic energy

So which has more energy? A swimming pool full of barely warm water, or ateaspoon of boiling hot water?

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

• Most H2O is in the form of water (liquid) on Earth’s surface (good for life)


• High latent (hidden) heats of

– Vaporization/condensation

– Melting/freezing

– Evaporation

• Latent heat is energy that goes into phase

change, not temperature change


• Water high heat capacity

– Amount of heat required to raise the temperature of 1 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

nnThatThat’’s why beachs why beach--sand is cold on an August nightsand is cold on an August night

but the water is still warmbut the water is still warm

• 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

Unique Properties of Water

Pure water vs. seawater

Hydrologic cycle describes recycling of water near Earth’s surface

Residence time and steady state

Water molecules in different states of matter

What are the condensationand vaporization points for pure water?

What are the freezing and melting 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)

• Freeze separation (like sea-ice)

Reverse Osmosis Water(‘RO’ water)

Commercial waterSupply plants

Dasani, Aquafina isRO water with some salts added back in(for flavor)

pH of Water

pH is a measure of the H+ concentration in waterpH = -log[H+]

dissociation of water H2O ↔H+ + OH-

for pure water, pH = 7.0 [H+] = 10-7 Mbut other solutes may add or remove H+ ions

in acidic solutions, pH = 0-7

in basic solutions, pH = 7-14


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, các tính chất này thể hiện yếu nên:

à chỉ các chất khử mạnh như kim loại kiềm, kiềm thổ

à chỉ các chất oxi hóa mạnh như 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

+ → +

+ → +


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

2 2

2

2

2 / /

0.0592 2 ( ) lg

2o

H H H HH

HH e H k

pε ε+ +

+

+ + = +É

( )2 2 2 2 2

4

2 2 / /

0.059( ) 4 4 2 ( ) lg

4o

O H O O H O OO k e H H O l p Hε ε+ + + + = + É

2 2

2

2 2

/

/

1

7

0.00

1.23

H O

o

H H

oO H O

p p atm

pH

V

V

ε

ε

+

= =

=

=

= 2/0.413

H HVε + = −

2 2/ 0.817O H O Vε =

Nước bị OXH

Nước bị KH

Không bKhông bịị OXH OXH -- KHKH


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

Chlorine 1.4


Chemical properties

98.74 /2 2 2 2-119.2 kJ/mol

2 2o

o

H kJ mol

GH O H O O∆ =−

∆ =→ + Z

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

peroxides.

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.)

In the presence of certain catalysts, such as Fe2+ or Ti3+, the decomposition may take a different path, with free radicals such as HO· (hydroxyl) and HOO· being formed. A combination of H2O2 and Fe2+ is known as Fenton's reagent.


Redox reactionsRedox reactionsIn 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 + 2 H+(aq) → 2 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 + 2 OH− → 2 Fe2+ + 2 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 Alkaline hydrogen peroxide is used for epoxidation of electron-deficient alkenes such as acrylic acids, and also for oxidation of alkylboranes to alcohols, the second step of hydroboration-oxidation.


Formation of peroxide compoundsFormation of peroxide compoundsHydrogen peroxide is a weak acid, and it can form hydroperoxide or peroxidesalts 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 + 4 H2O2 + 2 NaOH → 2 Na2B2O4(OH)4 + H2O

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

AlkalinityAlkalinityHydrogen peroxide is a much weaker base than water, but it can still form adducts

with very strong acids. The superacid HF/SbF5 forms unstable compounds containing the [H3O2]+ ion.


ManufactureHydrogen 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]

ConcentrationHydrogen 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 sale in small quantities to others.

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