pearson mastering biology ch 3
Which of the following is a hydrophobic material?
wax
How would you describe a buffer solution?
weak acid and its conjugate base
Why doesn't oil mix with water?
(c) Polar molecules attract one another. Water molecules cling to one another and won't part to make room for uncharged (nonpolar) molecules. There's no repulsion.
Which of the following can be attributed to water's high specific heat?
A lake heats up more slowly than the air around it.
Buffers work best when ...
about half of the buffer molecules are dissociated. (That arrangement results in the least change in pH when either acid or base is added.)
Which property of water allows a paper towel to pick up a puddle of water?
adhesion of water molecules to other kinds of molecules
The amount of energy that must be absorbed or lost to raise or lower the temperature of 1gram of liquid water by 1°C __________.
is 1 calorie
Which property of water allows a water strider to walk on water?
water's high surface tension
Which of the following best defines 'one kilocalorie'?
1,000 calories, or the amount of heat required to raise the temperature of 1 kg of water by 1°C
What will be the most likely change in pH when the H+ ions in the solution is increased to twice its original concentration?
1.6 to 1.3
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
Measurements show that the pHpH of a particular lake is 4.0. What is the hydrogen ion concentration of the lake?
10−4M
A slice of pizza has 500 kcalkcal. If we could burn the pizza and use all the heat to warm a 50-LL container of cold water, what would be the approximate increase in the temperature of the water? (Note: A liter of cold water weighs about 1 kgkg.)
10∘C
One mole (mol) of glucose (molecular mass = 180 daltons) is ________.
180 grams of glucose
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
Increased atmospheric CO2 concentrations might have what effect on seawater?
Seawater will become more acidic, and carbonate concentrations will decrease.
Which answer best describes why does ice float in liquid water?
Stable hydrogen bonds keep water molecules of ice farther apart than water molecules of liquid water.
Which of the following reasons explains why a steam burn is more severe than a hot water burn?
Steam contains more energy than water.
What is the pH of a solution with a hydroxyl ion (OH-) concentration of 10-10 M?
pH 4
The unequal sharing of electrons within a water molecule makes the water molecule _____.
polar
What kind of bond is formed between the two hydrogen atoms and the single oxygen atom?
polar covalent bonds
If a few drops of HCl is added to the buffer solution with the following equilibrium, ________.NH4+(aq) + H2O(1) ⇐ H3O+(aq) + NH3(aq)
the concentration of NH3 decreases but NH4+ increases
Consider two solutions: solution X has a pH of 4; solution Y has a pH of 7. From this information, we can reasonably conclude that ________.
the concentration of hydrogen ions in solution X is 1000 times as great as the concentration of hydrogen ions in solution Y
The partial negative charge in a molecule of water occurs because ________.
the electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen atom nucleus than around the hydrogen atom nucleus
Which property of water allows dogs to cool themselves by panting?
water's high heat of vaporization
Which of the following helps most to explain why water has a high specific heat?
(a) A water molecule can make 4 hydrogen bonds.(When you heat water, much of the heat is used to break hydrogen bonds. Only the remaining heat can increase molecular motion, raising the temperature.)
Which statement is true of water's tensile strength?
(a) It results from hydrogen bonding.(b) It helps to pull water through plants.(c) It involves both cohesion and adhesion.
Polar attractions are ...
(a) forces between atoms with partial charges.(b) weaker than covalent bonds.(c) important because they are numerous.
A buffer consists of undissociated acid (HA) and the ion made by dissociating the acid (A-). How does this system buffer a solution against decreases in pH?
) A- reacts with H+ to become HA. (A- binds most of the added H+, so not much H+ is left to lower the pH.)
When an ionic compound such as sodium chloride (NaCl) is placed in water, the component atoms of the NaCl crystal dissociate into individual sodium ions (Na+) and chloride ions (Cl-). In contrast, the atoms of covalently bonded molecules (e.g., glucose, sucrose, glycerol) do not generally dissociate when placed in aqueous solution. Which of the following solutions would be expected to contain the greatest number of solute particles (molecules or ions)?
1 liter of 1.0 M NaCl
Assume that acid rain has lowered the pH of a lake to pH 5.0. What is the hydroxide ion concentration of this lake?
1 × 10-9 mol of hydroxide ions per liter of lake water
Which answer helps to explain why all living cells need pH buffers?
Amino acid side chains have many carboxyl and amino groups. (When these side chains ionize, they exert forces that affect the protein's folding. Thus, if pH isn't stabilized, the proteins will change their folding and may not function properly.)
How does 0.5 M sucrose (molecular mass 342) solution compare to 0.5 M glucose (molecular mass 180) solution?
Both have 3.01 × 1023 molecules.
Identify all correct statements about the ionization of water.
Dissociation of water produces equal numbers of OH- and H+., Water ionizes to form hydroxide and hydronium ions., Dissociation of water is reversible.
How would acidification of seawater affect marine organisms?
It will decrease dissolved carbonate concentrations and hinder growth of corals and shell-building animals.
Consider the following reaction at equilibrium: CO2 + H2O ⇔ H2CO3. What would be the effect of adding additional H2O?
It would drive the equilibrium dynamics to the right.
How does the way a buffer stabilizes pH during addition of acid differ from the way the same buffer stabilizes pH during addition of base?
It's the same reaction running backward or forward.
Which factor is important in making it possible to cool yourself by sweating?
Molecules collide with varied angles and speeds.(b) Hydrogen bonds are relatively weak. (Random collisions allow some molecules to accumulate more energy than other molecules. The weakness of hydrogen bonds lets those molecules escape, leaving the cooler molecules behind.)
Which of the following is considered to be a strong base (alkali)?
NaOH →→ Na+ + OH-
Which statement must be mentioned in explaining why amphipathic molecules line up at a water surface?
Polar groups attract one another.
A beaker contains 100 milliliters (mL) of NaOH solution at pH = 13. A technician carefully pours into the beaker 10 mL of HCl at pH = 1. Which of the following statements correctly describes the result of this mixing?
The pH of the beaker's contents will decrease.
What happens when carbonate ion concentration in seawater decreases?
The rate of calcification decreases, and it takes longer for the reef coral to grow.
Which statement is true of pH buffers?
They consist of weak acids and weak bases.
Which statement helps to explain why ice is less dense than liquid water?
Water molecules make hydrogen bonds at definite angles.(b) Cold molecules move less than warm molecules.
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.
Dissolving is best described as ...
a mingling of molecules and/or ions.
Sodas typically contain flavorings, coloring agents, sugar, and carbon dioxide dissolved in water. The best term to describe this mixture would be __________.
an aqueous solution
The open spaces in water's crystal structure make it possible for ...
aquatic life to exist at the North Pole.
Many of water's emergent properties, such as its cohesion, high specific heat, and 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
Hydrogen bonds ...
can form between H and N.
The tendency of an atom to pull electrons toward itself is referred to as its _____.
electronegativity
What process exerts the pull on water molecules that is relayed from leaf to root via cohesion?
evaporation
A water molecule can bond to up to _____ other water molecules by ____ bonds.
four ... hydrogen
To make a buffer, you need to ...
have a weak acid or a weak base half ionized in water.
Because organisms are made primarily of water, they resist rapid temperature changes. This useful quality is based on water's __________.
high specific heat
Is the thermal energy of a full bathtub higher or lower than the thermal energy of a pot of freshly brewed coffee (even though the coffee has a higher temperature than the bathwater)? Why?
higher; greater volume
Water is a source of ______________ for chemical reactions in cells.
hydrogen and oxygen atoms
What kind of bonds are responsible for the unique cohesion, surface tension, and adhesion properties of water molecules?
hydrogen bonding
Water has surface tension because ...
hydrogen bonds between surface water molecules resist being stretched.
In a neutral solution the concentration of _____.
hydrogen ions is equal to the concentration of hydroxide ions
Melting of ice and thus reduced feeding opportunities for polar bears is occurring because of the ________.
increase in CO2 and other greenhouse gases in the atmosphere
An acid is a substance that __________.
increases the hydrogen ion concentration of an aqueous solution
Though you add heat, the temperature of boiling water remains constant because ...
it takes energy to break hydrogen bonds. (Correct! At boiling, all the added heat is used to break hydrogen bonds. Free of the water mass, the departing steam carries away all the added energy, with none left over to raise the temperature.)
A solution contains 0.0000001 (10-7) moles of hydrogen ions [H+] per liter. Which of the following best describes this solution?
neutral
Which of the following statements correctly describes the property of hydrophobic substances such as vegetable oil?
nonpolar substances that repel water molecules
Sulfur is in the same column of the periodic table as oxygen but it is less electronegative than oxygen. Compared to water molecules, how will the H2S molecules behave?
not be able to form hydrogen bonds with each other
We can be sure that a mole of table sugar and a mole of vitamin C are equal in their
number of molecules.
When carbon dioxide in the atmosphere dissolves with the raindrops, what is the expected change in pH of the raindrops?
slightly acidic
To act as an effective coolant in a car's radiator, a substance has to have the capacity to absorb a great deal of heat. Which physical property is the best indicator for a good coolant?
specific heat
Rank, from low to high, the pH of blood, stomach acid, and urine.
stomach acid, urine, blood
A solution of pH 7 is ________ than a solution of pH 8.
tens times as acidic
