geochem

Silicic Acid

H4SiO4

Hydrochloric acid

HCl

Nitric acid

HNO3

Sulfuric acid

H2SO4

Hydrosulfuric acid

H2S

Carbonic acid

H2CO3

Oxalic Acid

H2C2O4

Acetic acid

CH3COOH

Tap water pH

8.2

Rainwater pH

6.1

Ocean pH

7.5-8.2

Pure water pH

7

What are the top five reactions for controlling pH for natural waters

Photosynthesis (increase), respiration (decrease), dissolution (increase)/precipitation (decrease) of carbonate minerals, weathering of silicate minerals (increase), oxidation of pyrite (decrease)

Siderite

FeCO3

Barite

BaSO4

Dolomite

CaMg(CO3)2

Calcite

CaCO3

Aragonite

CaCO3

Fluorite

CaF2

Anhydride

CaSO4

Gypsum

CaSO4•2H2O

Halite

NaCl

What is the degree of saturation

ion activity product divided by ksp

What are the ways that natural waters can become supersaturated

1. Evaporative concentration, 2. Decrease in temperature, 3. Change in pH, 4. Mixing of waters, 5. Common ion effect

What is the precipitation sequence of evaporites

Calcite, Gypsum, Halite, K,Mg salts

Find each element name and common oxidation state (if necessary)

How can groundwater to increase in pH

The groundwater is under high pressure and isolated and contains dissolved carbon dioxide. After extraction, carbon dioxide escapes as a gas and increases pH