mastering biology online assignment chapter 3

Identify all correct statements about the ionization of water.

-Dissociation of water is reversible. -Water ionizes to form hydroxide and hydronium ions. -Dissociation of water produces equal numbers of OH- and H+.

The table shown here lists the specific heat of several substances. Substance Specific heat J/g/∘C water 4.18 ethyl alcohol 2.44 benzene 1.80 sulfuric acid 1.40 Based on the information in the table, which of the following statements are true?

-Sulfuric acid is less resistant to temperature change than water. -Benzene is more resistant to temperature change than sulfuric acid. -More heat is required to raise the temperature of 1 g of water 1 ∘C than to raise the temperature of 1 g of ethyl alcohol 1 ∘C. -Water has a high specific heat due to the hydrogen bonding between water molecules.

A pH of 6 is how many times more acidic than a pH of 9?

1,000 A pH of 6 is 10 times more acidic than 7, which is 10 times more acidic than 8, which is 10 times more acidic than 9. 10 x 10 x 10 = 1,000.

If the seawater carbonate ion concentration is 250 µmol/kg, a) what is the approximate rate of calcification, and b) approximately how many days would it take 1 square meter of reef to accumulate 30 mmol of calcium carbonate?

10 mmol CaCO3 per m2 per day; 3 days

If the seawater carbonate ion (CO3 2-) concentration is 270 µmol/kg, a) what is the approximate rate of calcification, and b) approximately how many days would it take 1 square meter of reef to accumulate 30 mmol of calcium carbonate (CaCO3)?

20 mmol CaCO3 per m2 per day; 1.5 days

If the molecular mass of a carbon atom is 12, the mass of a hydrogen atom is 1, and the mass of an oxygen atom is 16 daltons, how many molecules does one mole of table sugar (sucrose; C12H22O11) contain?

6.02 x 10^23, In fact, this is the number of molecules in one mole of any substance.

Select the statement that best describes a buffer.

A buffer resists change in pH by accepting hydrogen ions when acids are added to the solution and donating hydrogen ions when bases are added.

The concentration of the appetite-regulating hormone ghrelin is about 1.3 × 10-10 M in the blood of a fasting person. How many molecules of ghrelin are in 1 L of blood?

A liter of blood would contain 7.8 × 1013 molecules of ghrelin (1.3 × 10-10 moles per liter × 6.02 × 1023 molecules per mole).

Based on this graph, what is the relationship between carbonate ion concentration and calcification rate?

As the concentration of carbonate ions is increased, the rate of calcification increases.

Explain the pattern of temperatures shown in the diagram.

During the summer, the coastal areas are cooler than the inland areas because the ocean moderates the climate near the coast by absorbing and releasing heat.

Which of these bonds is weakest?

Hydrogen Bonds are weaker than covalent bonds because they do not involve sharing of electrons, and they are weaker than ionic bonds because they involve the attraction of partial (not full) opposite charges.

Why isn't this insect drowning?

Surface tension. (The high surface tension of water allows the insect to remain on the surface.)

What process exerts the pull on water molecules that is relayed from leaf to root via cohesion?

The evaporation of water from leaves moves water up from the roots via cohesion.

What happens when carbonate ion concentration in seawater decreases?

The rate of calcification decreases, and it takes longer for the reef coral to grow.

How does the pH of the solution on the right compare with that of the solution on the left?

The solution on the right is basic relative to the solution on the left. (The solution on the right has a lower concentration of hydrogen ions relative to hydroxide ions than does the solution on the left.)

Consider the hypothesis that increased atmospheric concentrations of CO2 will slow the growth of coral reefs, as the series of reactions in Figure 2 suggest. Do the results of the Biosphere 2 experiment support that hypothesis? Why or why not?

Yes; more CO2 dissolving into the oceans causes a decrease in the amount of CO3 2- in seawater, leading to a lower rate of calcification and slower reef growth.

Which property of water allows a paper towel to pick up a puddle of water?

adhesion of water molecules to other kinds of molecules Water adheres to the cellulose molecules in a paper towel, allowing the towel to pick up a puddle of water. This is similar to the adhesion between water molecules and cellulose in cell walls responsible for water transport in plants.

Classify each statement as an example of adhesion, cohesion, or surface tension. Drag each statement to the appropriate bin.

adhesion: -Water molecules cling to the side of a beaker. -Water molecules cling to plant cell walls. cohesion: -Water molecules are attracted to eachother -A drop of water spilled on a table forms a drop on the table, rather than spreading out over the surface. surface tension: -A sewing needle floats when it is placed gently on top of water in a bucket. -A water strider runs across a pond without breaking the surface.

Many of water's emergent properties, such as its cohesion, its high specific heat, and its high heat of vaporization, result from the fact that water molecules _____.

are attracted to each other by partial negative and positive charges on the oxygen and hydrogen atoms, respectively

Which variable is the dependent variable--the variable that responded to or depended on the treatment, and was measured by the researchers?

calcification rate

Which variable is the independent variable in this experiment--the variable that was manipulated by the researchers?

carbonate ion concentration in the seawater

The tendency of an atom to pull electrons toward itself is referred to as its _____.

electronegativity

Each water molecule is joined to _____ other water molecules by ____ bonds.

four ... hydrogen

Which step of the process shown in that figure was measured in the Biosphere 2 experiment?

fourth step

Because organisms are made primarily of water, they resist rapid temperature changes. This useful quality is based on water's _____.

high specific heat Water has a high specific heat, meaning that a relatively large amount of heat must be added or removed in order to get the temperature of the water to change significantly.

Water molecules have a polarity, which allows them to be electrically attracted to other water molecules and other polar molecules by weak chemical bonds known as _____.

hydrogen bonds, The polarity of a water molecule allows the oxygen of one water molecule to bond weakly to the hydrogen of another water molecule.

In a neutral solution the concentration of _____.

hydrogen ions is equal to the concentration of hydroxide ions

An acid is a substance that _____.

increases the hydrogen ion concentration of an aqueous solution

The amount of energy that must be absorbed or lost to raise or lower the temperature of 1 g of liquid water by 1°C _____.

is 1 calorie The specific heat of liquid water is 1 cal/g/°C.

The unequal sharing of electrons within a water molecule makes the water molecule _____.

polar

In this molecule, what type of bond is found between the oxygen and hydrogens?

polar covalent While oxygen shares electrons with hydrogen, the electrons spend more time with the oxygen than with the hydrogens.

What is shown on the y-axis, and in what units?

the calcification rate in millimoles of calcium carbonate (CaCO3) accumulated per square meter of reef per day

What is shown on the x-axis, and in what units?

the carbonate ion (CO3 2-) concentration of seawater, in micromoles per kilogram of seawater

Which property of water allows dogs to cool themselves by panting?

water's high heat of vaporization Evaporative cooling takes place when molecules with the greatest kinetic energy leave a fluid as gas molecules. Because of water's high heat of vaporization, a large amount of heat must be absorbed for 1 gram of water to be converted from liquid to gas. The dog loses this heat as the water on its tongue evaporates, allowing him to cool down by panting. To understand why this answer is correct, read about evaporative cooling.

Which property of water allows a water strider to walk on water?

water's high surface tension Water's high surface tension, related to its cohesion, makes water behave as though coated with an invisible film.