Download Marine Chemistry and Sediments Test Review

Oceanography
What is the Forchhammer’s
principle?
a. The saturation level of seawater
b.The constant proportion of solids in seawater
c. The components of seawater from weathering
surface rocks
d.The measure of the total mass of halogen ions
 Georg Forchhammer realized that even though oceans may have
varying salinity, dissolved solids are present in the ocean at
constant proportions. He also observed that there was less silica
and calcium in the ocean than in river water. These compounds
are removed by marine organisms. Information can be found in
the section Understanding the Ocean Began with Voyaging for
Trade and Exploration.
What is a solute?
A substance, usually a liquid, which dissolves other
substances
b) A substance that dissolves into another substance
c) A mixture of two or more substances
d) A polar molecule
a)
 In solutions, the solute is usually a dissolved solid or
gas. Generally, the concentration of a solute in a
solution is less abundant than the solvent. Information
can be found in the section Water Is a Powerful
Solvent.
What is not true of a mixture?
A mixture is different substances closely
intermingled.
b) A mixture is able to maintain separate properties.
c) A mixture is able to disperse homogenously.
d) A mixture may have varying concentrations and
properties throughout.
a)

A solution is heterogenously dispersed. The
substances in a mixture are not as evenly distributed
and keep their separate identities. Information can be
found in the section Water Is a Powerful Solvent.
What causes a decrease in oxygen
levels beyond the sunlit layer?
a) The respiration from marine animals and bacteria
b) The by-products of photosynthesis
c) There are fewer animals present
d) None of these choices
 The high level of oxygen at the surface is the byproducts of photosynthesis. Beyond that layer, the
oxygen decreases due to the respiration of marine
animals. At deep depths, oxygen levels increase
slightly because there are fewer animals at those
depths. Information can be found in the section
Gases Dissolve in Seawater.
What is not a factor on the salinity
of a particular region of ocean?
Evaporation
b) Precipitation
c) Freshwater run-off from the continents
d) Saturation levels
a)
 Salinity is the concentration of dissolved inorganic
solids in water. Despite an average of 35 0/00 salinity in
the ocean, there are regions of variation. Salinity levels
can be heavily impacted by evaporation, precipitation,
and run-off activities. Information can be found in the
section Seawater Consists of Water and Dissolved
Solids.
What type of water mass dissolves
the most amounts of gases?
a) Tropical water masses
b) Temperate water masses
c) Equatorial water masses
d) Polar water masses
 Gases dissolve the most in colder waters. The
saturation level increases as temperatures
decrease. This partly explains the high nutrient
productivity in the polar regions. Information can
be found in the section Gases Dissolve in Seawater.
What is the average length of time
an atom spends in the ocean?
Longevity
b) Saturation time
c) Residence time
d) Durability time
a)
 Residence time explains why the ocean does not
become progressively saltier with age. The residence
time of an element can be calculated by dividing the
amount of an element in the ocean by the rate at
which the element is added or removed from the
ocean. Information can be found in the section
Seawater Consists of Water and Dissolved Solids.
What enhances the ocean’s
buffering capacity?
a) The amount of dissolved inorganic carbon present
b) The amount of acid already present in the ocean
c) The amount of dissolved organic compounds
d) None of these choices

The ocean has a higher buffering capacity than rivers
and lakes. This is due to the amount of dissolved inorganic
carbon found in the ocean. This makes the ocean less
prone to large pH swings when acids or bases are added
whether it be from sewage outfalls or acid rain. Information
can be found in the section The Ocean’s Acid-Base Balance
Varies with Dissolved Components and Depth.
What is the colligative property of
osmotic pressure?
The pressure exerted on biological membranes from the
atmosphere
b) The pressure exerted on biological membranes from salinity
differences outside the cells
c) The pressure exerted on biological membranes during
temperature changes of water
d) The pressure exerted on biological membranes when
surrounding waters phase change
a)
 Osmotic pressure rises with increasing salinity. This
allows for the transmittance of water in and out of
cells. Information can be found in the section
Seawater Consists of Water and Dissolved Solids.
What is the greatest source of
oxygen in deep water?
a) The respiration from bacteria
b) The lack of large quantities of organisms
c) Chemosynthesis
d) Polar waters that have sunk from the surface
 Polar waters are very rich in nutrients, including
oxygen. This water sinks from the surface in these
regions and then circulated through deep water.
Information can be found in the section Gases
Dissolve in Seawater.
Water is able to dissolve ____ due
to its polarity.
a) covalent bonds
b) solvents
c) ionic bonds
d) Solutions
Ionic bonds are held together by their
electrostatic attraction between opposite charges.
Water’s polarity reduces this attraction until the
ions are able to be separated. Information can be
found in the section Water Is a Powerful Solvent.
What is the source of high carbon
dioxide levels at middle depths in
the ocean?
a) The decay of the remains of organisms
b) It diffuses from the atmosphere
c) Chemical reactions
d) Plant respiration
 Carbon dioxide levels in the middle depths of the
ocean are higher than they are at the surface.
Respiration from animals and the decay of the remains
of organisms are the large contributors to these high
levels of carbon dioxide. Information can be found in
the section The Ocean’s Acid-Base Balance Varies with
Dissolved Components and Depth.
Which element would be surprisingly
considered a trace element in the ocean
despite its abundance in the atmosphere?
a)
b)
c)
d)

Sodium
Calcium
Chloride
Nitrogen
Nitrogen is a trace element in the ocean despite its
abundance in the atmosphere. Any element that is less
than 1 part per million is considered a trace element.
Although trace elements are such small quantities, they are
often crucial to life processes. Information can be found in
the section Seawater Consists of Water and Dissolved
Solids.
What affects the residence time of
an element?
a) Its saturation level
b) Its chemical equilibrium in water
c) Its chemical activity in water
d) The principle of constant proportions

The residence time of an element is individual.
Some elements remain in seawater for short periods of
time before becoming bound in sediments. Chemical
activity of the element effects its residence time.
Information can be found in the section Seawater
Consists of Water and Dissolved Solids.
What is the source of most of the
dissolved materials found in the ocean?
a) Outgassing
b) Convection currents
c) Dissolving and weathering of crustal rocks
d) Biological activities
 Although there are multiple sources of the dissolved
materials in the ocean, much of the material comes from
the weathering of surface rocks from rain and waves. The
composition of the ocean is different from rivers because
there is the addition of excess volatiles coming from the
upper mantle. Information can be found in the section
Seawater Consists of Water and Dissolved Solids.
Which essential gas is often in an
unusable form in the ocean and
atmosphere?
a) Nitrogen
b) Oxygen
c) Carbon dioxide
d) All of these choices
 Nitrogen gas is saturates in the upper layers of the
ocean. Although organisms need nitrogen to build
proteins, most nitrogen cannot be used. The
nitrogen needs to be bound or fixed in order to be
used by organisms. Information can be found in
the section Gases Dissolve in Seawater.
The level of ____ increases with depth
which is a factor in the calcium
carbonate compensation depth.
a)
b)
c)
d)
Nitrogen
Oxygen
Carbon Dioxide
Ammonia
 Carbon dioxide concentrations are higher at deeper
depths. Contrastingly, oxygen levels decrease as the
depth decreases. This is true until middle depths of
the ocean; then, oxygen levels begin to increase again.
Information can be found in the section Gases
Dissolve in Seawater.
How was salinity measured before
the use of salinometers?
a) Silver nitrate was used to measure the chlorinity
b) The mass of the salts were measured after water
was evaporated
c) The conversion of sodium levels to salinity
based on equations
d) All of these choices
 Marine chemists used silver nitrate to measure the chlorinity
of a water sample. Equations were then used measure
convert the chlorinity to the salinity of the sample. The
procedure is calibrated against a known sample. Now
salinometers are used by measuring the electrical
conductivity. Information can be found in the section
Seawater Consists of Water and Dissolved Solids.
What happens to pH levels in
regions where there is more
carbon dioxide present?
a) Carbon dioxide does not heavily impact pH levels
b) The pH levels increase in these regions.
c) The pH levels decrease in these regions
d) The seawater is able to buffer enough that there is
no change.
 The pH level in the ocean can be altered in the ocean with
changes in carbon dioxide. Higher levels of carbon dioxide
which often occurs at middle depths in the ocean causes
the water to be less alkaline. Information can be found in
the section The Ocean’s Acid-Base Balance Varies with
Dissolved Components and Depth.
Why is the amount of carbon dioxide
dissolved in seawater much less than the
theoretical maximum saturation level?
a) Carbon dioxide is very soluble in water.
b) Carbon dioxide is able to form a weak acid when
combined with seawater.
c) Carbon dioxide is quickly used by photosynthetic
organisms.
d) Carbon dioxide moves quickly from the
atmosphere to the ocean.
 Carbon dioxide chemically combines with water quite
quickly which creates carbonic acid, but the low level in
comparison to the theoretical maximum saturation level is
due to photosynthetic organisms using it quickly.
Information can be found in the section Gases Dissolve in
Seawater.
Why does oil not dissolve in water?
a) It has covalent bonds connecting the atoms.
b) It is found within tissues of organisms.
c) It is not a polar molecule.
d) It has ionic bonds.

Oil molecules are nonpolar. Nonpolar
molecules are not attracted to water molecules so
the bond strength found in oil is not diminished as
it is with polar molecules. Information can be
found in the section Water Is a Powerful Solvent.
What factor allows for the carbon
present in sediments to re-enter back
into atmospheric and oceanic cycles?
a) Geological uplift
b) Acid rain
c) Sediments dissolving
d) All of these choices
 Geological uplift can expose carbonate rock to
chemical reactions with oxygen. Acid rain on
limestone rock can release carbon dioxide. Lastly,
sediments can also dissolve which would release the
carbon dioxide that is stored in it. Information can be
found in the section Gases Dissolve in Seawater.
What is the approximate mixing
time of the ocean?
a) 160 years
b) 1,600 years
c) 16,000 years
d) None of these choices
 The mixing time of the ocean is due to vigorous
current activity. This activity allows constituent
materials to become evenly distributed throughout
the ocean. Information can be found in the section
Seawater Consists of Water and Dissolved Solids.
What does carbon dioxide break
down into once it is in the ocean?
a) Carbonic acid
b) Bicarbonate
c) Carbonate
d) All of these choices
 Carbon dioxide is able to form different compositions
when dissolved in water. First, it creates carbonic acid,
a weak acid. The acid then disassociates into
bicarbonate and carbonate. Information can be found
in the section The Ocean’s Acid-Base Balance Varies
with Dissolved Components and Depth.
What is the average pH of the
ocean?
a)
b)
c)
d)
7.0
7.5
8.0
8.5
 Although the pH can vary in particular regions and
depths of the ocean, the average pH is 8.0. The amount
of carbon dioxide can have large impacts on the pH
levels. The range of pH found in the ocean is
approximately 7.0 to 8.5. Information can be found in
the section The Ocean’s Acid-Base Balance Varies with
Dissolved Components and Depth.
What is diffusion?
a) The rate at which solute molecules present in a
solution is equal to the rate they are being
dissolved
b) The reforming of crystals
c) The amount of substances tied to biological cycles
d) The random movement of materials through a
solution
 Dissolved substances move randomly through a solution
due to diffusion. These substances do, however, move from
areas of high concentrations to areas of low concentrations.
Eventually, the result of diffusion is an evenly distributed,
homogenous solution. Information can be found in the
section Water Is a Powerful Solvent.
How do salinometers measure
salinity?
a) It measures the number of salt molecules in a set mass
of seawater.
b) It calculates the salinity based on the density of the
seawater.
c) It measures the electrical conductivity of seawater
samples.
d) It calculates the salinity by measuring the chlorinity.
 The conductivity of seawater varies with salt
concentrations and temperatures. Salinometers are
able to adjust for the water temperature and be
calibrated against samples of known conductivity and
salinity. Information can be found in the section
Seawater Consists of Water and Dissolved Solids.
Which item is not considered to
have a basic pH?
a) Seawater
b) Black coffee
c) Household ammonia
d) Baking soda
 Many of the foods and liquids we consume are
acidic. Black coffee and sodas are acidic. Seawater
and the other items listed above are alkaline, or
basic solutions. Information can be found in the
section The Ocean’s Acid-Base Balance Varies with
Dissolved Components and Depth.
What is the term for ocean components
not accounted for by the weathering of
continents?
a) Conservative constituents
b) Excess volatiles
c) Nonconservative constituents
d) Trace elements
 Excess volatile are the components in the ocean that
are not form the weathering of continents as the
conservative constituents. These appear to be from the
upper mantle. Information can be found in the section
Seawater Consists of Water and Dissolved Solids.
Why are some tropical waters
unable to sustain life?
a) There is an addition of pollutants in many of these
areas.
b) There is a low level of dissolved oxygen due to
temperature.
c) There is a greater amount of carbon dioxide.
d) There are more conservative components in these
waters.
 Gases dissolve readily in cold waters. Tropical waters have
lower saturation capabilities. The oxygen concentrations in
some tropical regions may not be able to sustain animals.
This can be further affected by the addition of pollutants
from sewage. Information can be found in the section
Gases Dissolve in Seawater.