Deck 5: The Chemistry of Seawater

Question 1

Instruments used to measure the electrical conductivity of seawater can produce continuous readings of salinity with depth or continuous readings of salinity with time at a fixed depth.

Answer 1

True

Question 2

Carbon dioxide concentrations in seawater increase with depth.

Answer 2

True

Question 3

More oxygen is found in surface waters at lower latitudes than in surface waters at polar latitudes.

Answer 3

False

Question 4

The chemical constituents of sea salt that are not utilized or altered by biological processes are called nonconservative.

Question 5

Salinity of seawater is approximately equal to the total dissolved salts in seawater expressed as grams of salt per kilogram of seawater.

Question 6

Seawater percolating through the fractured crust along ridge systems acts to both remove salts from and add salts to seawater.

Question 7

Nutrients and dissolved gases in seawater are considered conservative substances.

Question 8

The polar nature of water molecules aids in water's solvent abilities.

Question 9

The salinity of a water sample can be determined by multiplying its ________ by 1.80655.

Question 10

The rule of constancy of composition of sea salts for open-ocean water specifies that regardless of the salinity, the major ions always appear in the same ratio to each other.

Question 11

Identify the four seawater constituents that are present in the highest concentration.

A) magnesium
B) bromide
C) sodium
D) chloride
E) calcium
F) potassium
G) sulfate

Question 12

The dissolving ability of water is related to ________.

A) the attraction between the water molecule's positive and negative charges and charges on other atoms
B) its ability to form hydrogen bonds with other molecules
C) its ability to transmit energy from water molecule to water molecule
D) the attraction between the water molecule's positive and negative charges and charges on other atoms and its ability to form hydrogen bonds with other molecules
E) the attraction between the water molecule's positive and negative charges and charges on other atoms, its ability to form hydrogen bonds with other molecules, and its ability to transmit energy from water molecule to water molecule

Question 13

An ion with a positive charge is called a(n) ________

Question 14

Anoxic water contains too much oxygen.

Question 15

In the process called osmosis, water naturally travels through a semipermeable membrane from the side of low salt concentration to the side of high salt concentration.

Question 16

Cold seawater holds less oxygen than warm seawater at the same pressure and salinity.

Question 17

Formation of evaporites acts to add salts to seawater.

Question 18

The process of reverse osmosis uses pressure to separate fresh water from salt water through a semipermeable membrane.

Question 19

When the salinity of a seawater sample changes, the ratio of the major salt ions does not change.

Question 20

The relative molar abundance of carbon, nitrogen, and phosphorus in marine phytoplankton can be expressed in a relationship called the ________ ratio.

Question 21

When salt-forming ions are placed in water, they combine with each other and form solids.

Question 22

If a chemical is not very abundant in the ocean but has a high rate of delivery to the ocean from land sources, it will have a ________ residence time in the ocean and will ________ become part of the seafloor sediments.

A) long; quickly
B) long; slowly
C) short; quickly
D) short; slowly
E) variable; variably

Question 23

The oceans are a major contributor of oxygen to the earth's atmosphere.

Question 24

An ion with a negative charge is a cation.

Question 25

The average salinity of the oceans is about ________ parts per thousand (‰).

A) 30
B) 35
C) 37
D) 40
E) 45

Question 26

The proportions of the major salts in seawater are constantly changing.

Question 27

The percentage of oxygen dissolved in seawater is greater in surface waters than in the deep ocean.

Question 28

If the salinity of ocean water is 36‰, there are ________ g of salt left from evaporating 2 kg of seawater.

A) 9
B) 18
C) 36
D) 54
E) 72

Question 29

The major ionic constituents of sea salt are normally found to ________.

A) have a constant ratio of each constituent to each other
B) behave as conservative materials
C) have the same ratio to each other even when diluted by rainwater
D) All of these are correct.
E) None of these is correct.

Question 30

Acid rain falling on seawater has little effect on the pH of the oceans.

Question 31

The saturation value of oxygen in seawater increases as the temperature increases.

Question 32

Which situations cause an ion to have a long residence time in the oceans?

A) A high rate of ion addition
B) A rapid rate of reaction with other substances
C) Small total amount of ion present
D) A high rate of ion addition and a rapid rate of reaction with other substances acting together
E) None of these is correct.

Question 33

Surface salinities at high latitudes tend to be greater in summer than winter.

Question 34

Sources of the oceans' salts are believed to include ________.

A) Earth's crust
B) Earth's early atmosphere
C) volcanic eruptions
D) Earth's crust and Earth's early atmosphere
E) Earth's crust, Earth's early atmosphere, and volcanic eruptions

Question 35

Surface values of dissolved oxygen may exceed 100% saturation.

Question 36

Ions are removed from seawater most effectively by ________.

A) evaporation
B) freezing
C) adsorption
D) bacterial action
E) None of these is correct; one method is not more effective than another.

Question 37

Electrical conductivity readings at a known temperature measure ________.

A) salinity
B) temperature
C) pressure
D) viscosity
E) density

Question 38

Salinity may be measured by checking the water's ________.

A) viscosity
B) temperature
C) conductivity
D) pressure
E) surface tension

Question 39

Dittmar analyzed approximately seventy seawater samples collected around the world during the Challenger Expedition. He concluded that ________.

A) seawater had the same salinity worldwide
B) salt content changes due to processes that add or subtract salt
C) the major ions were always present in the same ratios
D) dissolved gases are always present in the same ratios
E) the major ions were always present in the same ratios and dissolved gases are always present in the same ratios

Question 40

An ion with a positive charge is known as a cation.

Question 41

Sources of oxygen in the open sea include ________.

A) the atmosphere
B) photosynthesis
C) respiration and decay
D) the atmosphere and photosynthesis
E) photosynthesis and respiration and decay

Question 42

Which of the following chemicals is commercially extracted from seawater?

A) Sulfur
B) Gold
C) Manganese
D) Bromine
E) Phosphate

Question 43

The pH of seawater is regulated by its ________.

A) carbon dioxide concentration
B) oxygen
C) temperature
D) pressure

Question 44

Which of the following ions has the highest concentration in seawater?

A) Na⁺
B) Cl^-
C) Mg²⁺
D) K⁺
E) Ca²⁺

Question 45

The concentration of carbon dioxide in surface water is low, whereas the concentration of oxygen is high because of the ________.

A) difference in solubility of the gases
B) exchange of gases between the atmosphere and the ocean
C) photosynthesis process
D) respiration of plants and animals
E) conversion of carbon dioxide to bicarbonate

Question 46

Which of these processes results in the transfer of the carbon from carbon dioxide to the deep sea?

A) Photosynthesis
B) Respiration
C) Decay
D) Photosynthesis and decay
E) Photosynthesis, respiration, and decay

Question 47

Trace elements in seawater are ________.

A) toxic to marine life forms
B) necessary for many marine life forms
C) found in concentrations suitable for commercial use
D) significant components of the total salt content of seawater
E) in higher concentrations at lower salinities

Question 48

Which desalination process requires the least energy?

A) Reverse osmosis
B) Distillation
C) Ion exchange
D) Freezing
E) Electrodialysis

Question 49

Electrodialysis produces ________ from low-salinity seawater.

A) bromine and magnesium
B) energy
C) fresh water
D) oxygen and carbon dioxide
E) table salt (sodium chloride)

Question 50

Which ion has the shortest residence time in the oceans?

A) Chloride
B) Sodium
C) Potassium
D) Sulfate
E) Iron

Question 51

Nutrients are nonconservative constituents of seawater because they ________.

A) maintain constant ratios to each other
B) do not maintain constant ratios to each other
C) are recycled into plants and animals
D) maintain constant ratios to each other and are recycled into plants and animals
E) do not maintain constant ratios to each other and are recycled into plants and animals

Question 52

The residence time of an ion in the oceans may be determined by ________.

A) multiplying the input rate by the output rate
B) multiplying the total amount of the ion by either the input or output rate
C) dividing the total amount of the ion by either the input or output rate
D) dividing the ionic concentration by the input or output rate
E) multiplying the ionic concentration by the total amount of the ion

Question 53

Carbon dioxide in seawater keeps the water's pH ________.

A) slightly alkaline
B) strongly alkaline
C) slightly acid
D) strongly acid
E) neutral

Question 54

The total change in concentration of carbon dioxide with depth is small because ________.

A) carbon dioxide combines with water to form carbonic acid and bicarbonate
B) decay occurs at all depths
C) photosynthesis occurs only at the surface
D) carbon dioxide is added directly from the atmosphere
E) carbon dioxide reacts with oxygen

Question 55

Which latitudinal area tends to have the highest average surface salinity?

A) Polar areas (80° to 90°)
B) Equatorial areas (0° to 10°)
C) Tropics (25° to 30°)
D) Midlatitudes (60°)
E) None of these is correct.

Question 56

Which gas has the highest concentration throughout the entire ocean?

A) Oxygen
B) Carbon dioxide
C) Nitrogen
D) Argon
E) Concentrations vary with time.

Question 57

Seawater taken from an area with a large, growing plant population has a ________.

A) low CO₂ and high nutrient content
B) low O₂ and low nutrient content
C) high O₂ and low nutrient content
D) high O₂ and high CO₂ content
E) None of these is correct.

Question 58

The depth at which the rate of photosynthesis balances the rate of plant respiration is known as the ________.

A) saturation value depth
B) compensation depth
C) gas equilibrium depth
D) photosynthesis cutoff depth
E) None of these is correct.

Question 59

The rate at which the oceans absorb carbon dioxide is controlled by ________.

A) temperature, salinity and pressure
B) pH
C) mixing and circulation processes
D) temperature, salinity and pressure, pH, and mixing and circulation processes

Question 60

A device used to separate fresh water from salt water using heat is called a(n) ________.

A) osmometer
B) dialysis machine
C) still
D) ion exchange column
E) salt fountain

Question 61

As we go below the euphotic zone of the open ocean and into greater depths, ________.

A) oxygen increases with depth
B) carbon dioxide increases with depth
C) photosynthesis increases with depth
D) respiration decreases with depth
E) None of these is correct

Question 62

The balance between photosynthesis and respiration in the open ocean's water column ________.

A) changes with depth
B) favors photosynthesis for most of the euphotic zone
C) is affected by light availability
D) All of these are correct.
E) None of these is correct.

Question 63

An average value for the salinity of seawater could be (pick the best choice).

A) 15 g/kg
B) 20 g/kg
C) 25 g/kg
D) 30 g/kg
E) 35 g/kg

Question 64

The depth at which the rate of photosynthesis balances the rate of respiration is called the ________ depth.

Question 65

Sea surface salinity is a function of ________ and ________.

Question 66

Which of the following is NOT a major dissolved constituent of seawater?

A) Iron
B) Chloride
C) Sodium
D) Magnesium
E) Potassium

Question 67

Carbon dioxide is added to seawater by ________.

A) photosynthesis
B) respiration
C) decomposition
D) transfer from the atmosphere
E) respiration, decomposition and transfer from the atmosphere

Question 68

Check each of the following constituents of seawater that are conservative constituents.

A) Sodium
B) Oxygen
C) Sulfate
D) Carbon dioxide
E) Phosphorus
F) Chloride

Question 69

Major ions constitute ________.

A) 100% of all ions in seawater
B) 99.3% of all ions in seawater
C) 95.3% of all ions in seawater
D) 91.3% of all ions in seawater
E) 50% of all ions in seawater

Question 70

Profiles of the concentration of oxygen and carbon dioxide in seawater from the surface to a depth of about 800 m are mirror images of each other.

Question 71

The Redfield ratio ________.

A) is related to the average composition of all plankton in the ocean
B) was originally formulated to relate carbon, oxygen, and hydrogen
C) is of no practical importance to oceanography today
D) All of these are correct.
E) None of these is correct.

Question 72

The salinity of surface waters in the oceans ________.

A) varies mainly in response to the balance between evaporation and precipitation at a given locality
B) varies mainly in response to the intensity of winds at a given locality
C) varies mainly in response to variations in the depth of the euphotic layer
D) is everywhere the same
E) varies chaotically

Question 73

In order to change the pH of water by one integer number (from 7 to 8 or from 8 to 7, for instance), you would have to change the concentration of the hydrogen ion by a factor of ________.

A) 1000
B) 500
C) 100
D) 50
E) 10

Question 74

An ion with a negative charge is called a(n) ________.

Question 75

The biological pump ________.

A) refers to the heaving and hoeing of whales
B) removes particles from the surface ocean to greater depths
C) removes the majority of particles generated in the surface ocean through photosynthesis
D) All of these are correct.
E) None of these is correct.

Question 76

The major ions of seawater are those which ________.

A) are used by living organisms to build their soft tissues
B) have residence times that are short relative to the mixing time of the oceans
C) do not vary from place to place in the oceans, except as salinity varies
D) None of these is correct
E) All of these are correct

Question 77

The residence time of iron and sodium in the oceans is approximately the same.

Question 78

The ratio of chlorine to sodium in seawater is about 1.8.

Question 79

The process of adherence of ions and molecules onto a particle's surface is called ________.

Question 80

Oxygen (O₂) ________.

A) is not affected by photosynthesis
B) is typically found in the lowest concentrations where photosynthesis takes place
C) is of no use whatsoever to any organism in the euphotic zone
D) All of these are correct
E) None of these is correct