Part 2. The Hydrosphere

Part 2. The Hydrosphere

Chapter 9. The Hydrosphere

 Distribution of Hydrosphere

Chapter 9. The hydrosphere

9.0 The hydrosphere: generals

 Fresh water Distribution in the ground

Only 1% of all fresh water (=0.03% of Earth’s total water supply): dominates studies in environmental chemistry, because it is readily available and essential requirement for the survival and growth of many forms of animal and plant life on the planet.

9.0 The hydrosphere: generals

Chapter 9. The hydrosphere

 Structure of Ice

Density of Ice = 0.917 kgL^-1

Enthalpy of fusion = 6.02 kJmol^-1

On melting, , meaning that liq. water at

0 ⁰C retains a considerable component of the ice structure.

9.1 Physical and chemical properties of water: Ice and liquid water

Chapter 9. The hydrosphere

 Water has one of the largest constants, meaning good solvent

for .

 : water molecules orient themselves around ions

 Degree of hydration (Hydration number) depends on:

-the charge to radius ratio (see Tab. 9.2): most influential factor

9.1 Physical and chemical properties of water: Hydration

Chapter 9. The hydrosphere

 ‘Aquo’ complexes: hydrated ions

 Stability of complexes: expressed by stability constants (or formation constants)

M + L ML ML + L ML₂ ML₂ + L ML₃ ML₃ + L ML₄

Overall rxn M + 4L ML₄

    

1 ML / M L Kf 

    

2 ML / ML L2

Kf 

    

3 ML / ML3 2 L Kf 

    

4 ML / ML4 3 L Kf 

    

⁴

4 ML4 / M L

 











4 Kf1 Kf 2 Kf3 Kf4

    

If no. of ligands bound to the metal ion=n, then _n  K_f1 K_f2 K_f3  K_fn E.g. in the ocean,

9.1 Physical and chemical properties of water: Complexation

Chapter 9. The hydrosphere

O H aq

Cl O H Hg aq

Cl aq

O H

Hg( ₂ )₆^2( )4 ^( )  ( ₂ )_{2 4}^2( )4 ₂

 Water: substance, undergoing autoprotolysis to form H₃O⁺ and OH^- ions

 E.g. acidification of water, by e.g. oxalic acid, being the degradation products of natural organic matter (NOM)

1.01 10 14at 25 Kw   ^ ℃

2 1

3 2

2 ( ) ( ) 5.6 10

)

(COOH H O  COOHCOO^ aq H O^ aq K_a   ^

5 2

3 2

2 ( ) ( ) ( ) 5.2 10

)

( ^{  }

 aq  H O  COO aq  H O aq K_a  

COOHCOO



 



 O H O aq e O

H 4 ( ) 4

6 _{2 2 3}



  

 e H OH O

H 2 2

2 _{2 2}

25℃ 051

. 0 23 .

1 pH at

E  

25℃ 0591

.

0 pH at E 

9.1 Physical and chemical properties of water: Acid-base properties

9.1 Physical and chemical properties of water: Redox properties

Chapter 9. The hydrosphere

) ( )

(

2H₂O  H₃O^ aq OH ^ aq