Chapter 9 - Alkalinity

Question 1

Speciation of CO2 versus pH

Answer 1

H2CO3 : high concentration with low pHs, declines at 3.6
HCO3- : concentrations begin to increase at 3.6 and peaks at 8.3, then declines after that where it will hit a pH of 12 and have no concentration left
CO32- : concentrations begin to increase at 8.3, and hits a peak at pH 12

Question 2

Co2 is _____ (acidic or basic)

Answer 2

acidic

Question 3

Excess CO2 does what to the ocean’s acidity?

Answer 3

Increases it and acidic conditions make it harder for some species to survive. CO2 is corrosive to the shells and skeletons of many marine organisms

Question 4

Total alkalinity

Answer 4

The total concentration of titratable bases expressed as calcium carbonate. Calcium carbonate is the basis for alkalinity as it is usually added to increase pH and alkalinity of acidic water (pond liming)

Question 5

What are the two types of alkalinities

Answer 5

P and T alkalinities

Question 6

P alkalinity

Answer 6

Phenolphthalein endpoint at pH 8.3 (pink)

Question 7

T alkalinity

Answer 7

Methyl orange endpoint pH T4.5 (orange)

Question 8

Total alkalinity analysis

Answer 8

Determined by titration of water sample with standard sulfuric acid

Question 9

Sources of alkalinity

Answer 9

Carbonate makes up most of the total alkalinity due to the common occurrence and dissolution of carbonate rocks and CO2 in the atmosphere. Other sources: dissolved ammonia borate, phosphate etc.

Question 10

Buffers

Answer 10

Consists of a mixture of weak acid and its conjugate base or a weak base and its conjugate acid

Question 11

Low alkalinity waters = ____ buffering capacity

Answer 11

Low

Question 12

Waters with total alkalinity 0-50 mg/L are usually

Answer 12

Less productive