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Chapter 3 Water: Homework
1) The atoms in a water molecule are held together by covalent bonds. This means that the bonded atoms
2) Which statement is true about hydrogen bonds between water molecules? A) They are about as strong as the covalent bonds in a water molecule. B) They arise because of the linear geometry of water. C) They cause water to have an unusually low freezing point for its molecular weight. D) They involve the unequal sharing of a proton between water molecules. E) In liquid water the same molecules attract to each other over long time periods.
3) The abundance of water in the cells and tissues helps to minimize temperature fluctuations. This is due to what property of water? A) Density. B) Viscosity. C) Specific heat. D) Boiling point.
4 ) Compounds that ionize when dissolved in water are called ________. A) electrolytes B) polar compounds C) hydrophobic compounds D) amphipathic compounds 5) Poorly soluble molecules such as lipids and nucleoside bases can be made more soluble in cells by attaching ________ to them. A) water B) oxygen C) carbohydrates D) salt ions 6) Electrolytes dissolve readily in water because A) they are held together by electrostatic forces. B) they are hydrophobic. C) water molecules can cluster about cations. D) water molecules can cluster about anions. E) water molecules can cluster about cations and anions. 7) A molecule or ion is said to be hydrated when it ________. A) is neutralized by water B) is surrounded by water molecules C) reacts and forms a covalent bond to water D) aggregates with other molecules or ions to form a micelle in water 8) If liquid A is more polar than liquid B, you might expect
Liquid A to evaporate faster than liquid B
Liquid A to evaporate more slowly than liquid B
Liquid A and liquid B to evaporate at the same rate
d) Liquid B to be colored
9) Solutes diffuse more slowly in cytoplasm than in water because of A) the higher viscosity of water. B) the higher heat of vaporization of water. C) the presence of many crowded molecules in the cytoplasm. D) the absence of charged molecules inside cells. 10) The ________ pressure is the pressure required to prevent the flow of solvent through a solvent-permeable membrane that separates two solutions of different solute concentration. A) hydrostatic B) electromotive C) osmotic D) partial 11) Which is true about the solubility of electrolytes in water? A) They are all insoluble in water. B) They are usually only sparingly soluble in water. C) They often form super-saturated aqueous solutions. D) They readily dissolve and ionize in water.
12) The water molecule is
Slightly negative near the hydrogen atoms and slightly positive near the oxygen atom
Slightly positive in all areas of the molecule
Slightly negative near the oxygen atom and slightly positive near the hydrogen atoms
The same charge in all areas of the molecule
13) A paper clip can stay on the surface of a sample of water because of water’s strong surface tension. Water’s surface tension is mostly a result of
The motion of water molecules
The attraction of water molecules
The impurities in the water
14) Sodium chloride is made up of sodium ions and chloride ions which bond together in a salt crystal because
They have the same charge
They are the same size
One is positive and one is negative so they attract
They both have protons and electrons
15) Water is able to dissolve sodium chloride because
The polar areas of water molecules attract the oppositely charged ions of sodium chloride
The shape of the water molecules pushes the sodium and chloride ions apart
The oxygen in the water molecules reacts with the sodium and chloride ions
Water molecules and sodium chloride are covalently bonded
16) Water cannot dissolve all substances that are made from ionic bonds. This is probably because
Some water molecules are not as strong as others
Water needs to be stirred to dissolve all ionic substances
Some ionic bonds are too strong for the attractions of water molecules to pull them apart
Water needs to be heated to dissolve all ionic substances
17) The chemical formula for sucrose (sugar) is C6H12O6. In some parts of the sucrose molecule, oxygen is covalently bonded to hydrogen. This makes the sucrose molecule
Bonded like salt
Smaller than a water molecule
A polar molecule
Act like a liquid
18) Sucrose dissolves well in water because
Water is usually warm
Sucrose is used to make sweet beverages
Polar water molecules attract the opposite polar areas of the sucrose molecules
Polar water molecules attract the carbon atoms in the sucrose molecules
19) When sucrose dissolves in water
The sucrose molecules break apart into individual atoms
The water molecules covalently bond to the sucrose molecules
The water molecules cause the sucrose molecules to separate from one another
Each sucrose molecule breaks in half
20) Alcohol molecules are not as polar as water molecules. If you mixed sucrose in alcohol you might expect the sucrose
To dissolve better in alcohol than in water
To dissolve in alcohol not as well as in water
To dissolve equally well in alcohol and in water
To increase in size
21) Water is not a good dissolver of oil mainly because
Oil is also a liquid
Oil is thicker than water
Oil molecules are non-polar
Oil is colder than water
22) Carbon dioxide gas dissolves pretty well in water because
The molecules of a gas are far apart compared to the molecules of a liquid
The bond between the carbon and oxygen in the carbon dioxide is polar
Water can dissolve anything with carbon
Water molecules are non-polar
23) The amount of gas that can dissolve in water
Increases as the temperature of the water increases
Increases as the temperature of the water decreases
Does not change when the temperature of the water changes
Does not depend on the type of gas
24) When certain substances dissolve, the solution gets warmer. This type of dissolving process is exothermic. In exothermic dissolving
More energy is released when water molecules bond to the solute than is used to pull the solute apart.
More energy is used to pull the solute apart than is released when water molecules bond to the solute.
A gas is always produced
The temperature does not change
25) When certain substances dissolve, the solution gets colder. This type of dissolving process is endothermic. In endothermic dissolving
Water molecules break apart into atoms
26)What does it mean to say that something is a “polar molecule”?
A polar molecule has a net dipole as a result of the opposing charges (i.e. having partial positive and partial negative charges) from polar bonds arranged asymmetrically. Water (H2O) is an example of a polar molecule since it has a slight positive charge on one side and a slight negative charge on the other.
27) What is surface tension and why does water have a strong surface tension?
In a sample of water, there are two types of molecules. Those that are on the outside, exterior, and those that are on the inside, interior. The interior molecules are attracted to all the molecules around them, while the exterior molecules are attracted to only the other surface molecules and to those below the surface. This makes it so that the energy state of the molecules on the interior is much lower than that of the molecules on the exterior. Because of this, the molecules try to maintain a minimum surface area, thus allowing more molecules to have a lower energy state. This is what creates what is referred to as surface tension.
28) You put a drop of water and a drop of alcohol on a paper towel and saw that the alcohol evaporated faster than the water. Alcohol molecules are not as polar as water molecules. Use the difference in polarity between water and alcohol molecules to explain why alcohol evaporates faster than water.
A more polar molecule will have stronger attractive forces between its molecules than a liquid with weaker polarity. It will require more energy to break the lattice of the liquid with the greater polarity. Therefore alcohol will require less energy to break its lattice and evaporate faster.
29) The surface of water bends but doesn’t break under the weight of a paper clip or water strider. What is it about water molecules and the way they interact that gives water this strong surface tension?
The strong polarity of water will produce large numbers of hydrogen bonds forming a strong lattice.
30) You put drops of water and alcohol on the surface of two pennies. The water held together and beaded up more than the alcohol. Also, more drops of water than alcohol stayed on the penny. If water molecules are more polar than alcohol molecules, explain why this happened.
The strong polarity of water will produce large numbers of hydrogen bonds forming a strong lattice. This will keep the water molecules together forming a bead.
31) Briefly explain, on the molecular level, how water dissolves salt.
On addition to water the Na+ section of NaCl is attracted to the oxygen side of the water molecules, while the Cl- side is attracted to the hydrogens' side of the water molecule. his causes the sodium chloride to split in water, and the NaCl dissolves into separate Na+ and Cl- atoms. A hydration shell is formed around them which prevents Na+ and Cl- to form ionic bonds.
32) Why does water dissolve salt more effectively than isopropyl alcohol does?
Water is more polar than isopropyl alcohol.
33) Why does sugar not dissolve in mineral oil?
Mineral oil is a lipid and is nonpolar. Sugar is a polar molecule. Polar molecules will not dissolve in nonpolar liquids..
34) Why does increasing the temperature cause more solute to dissolve in a solvent?
The movement of the molecules (kinetic energy) in a solvent increases with increasing temperature. The force of the collisions with a solute are greater enabling the solute to dissolve faster.
35) What are the four emergent properties of water that are important for life?
cohesion, expansion upon freezing, high heat of evaporation, capillarity
cohesion, moderation of temperature, expansion upon freezing, solvent properties
moderation of temperature, solvent properties, high surface tension, capillarity
heat of vaporization, high specific heat, high surface tension, capillarity
polarity, hydrogen bonding, high specific heat, high surface tension
36) Water shows high cohesion and surface tension and can absorb large amounts of heat because of large numbers of which of the following bonds between water molecules?
strong ionic bonds
nonpolar covalent bonds
polar covalent bonds
weak ionic bonds
37) Water has an unusually high specific heat. What does this mean?
At its boiling point, water changes from liquid to vapor.
More heat is required to raise the temperature of water.
Ice floats in liquid water.
Salt water freezes at a lower temperature than pure water.
Floating ice can insulate bodies of water.
38) In a glass of old-fashioned lemonade, which is the solvent?
39) Compared to an acidic solution at pH 5, a basic solution at pH 8 has
1.000 times more hydrogen ions.
1.000 times less hydrogen ions.
100 times less hydrogen ions.
the same number of hydrogen ions but more hydroxide ions.
100 times less hydroxide ions.
40) Which of the following acts as a pH buffer in blood?
A and B
41) Scientists predict that acidification of the ocean will lower the concentration of dissolved carbonate ions (CO32), which are required for coral reef calcification. To test this hypothesis, what would be the independent variable?
the rate of calcification
the amount of atmospheric CO2
volume of seawater
42) Based on this graph, what is the relationship between carbonate ion concentration and calcification rate?
As the acidity of the seawater increased, the rate of calcification decreased.
As the rate of calcification increased, the concentration of carbonate ions increased.
As the concentration of carbonate ions increased, the rate of calcification decreased.
As the concentration of carbonate ions increased, the rate of calcification increased.
43) If the seawater carbonate ion concentration is 250 µmol/kg, what is the approximate rate of calcification according to this graph?
5 mmol CaCO3 per m2 per day
10 mmol CaCO3 per m2 per day
15 mmol CaCO3 per m2 per day
20 mmol CaCO3 per m2 per day
44) This figure suggests that increased atmospheric concentrations of CO2 will slow the growth of coral reefs. Do the results of the previous experiment support that hypothesis?
No; more atmospheric CO2 causes a decrease in the amount of CO32 in seawater, leading to faster reef growth.
Yes; more CO2 causes an increase in the amount of CO32 in seawater, leading to slower reef growth.
No; more atmospheric CO2 causes an increase in the amount of CO32 in seawater, leading to faster reef growth.
Yes; more CO2 causes a decrease in the amount of CO32 in seawater, leading to slower reef growth.
45) In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by _____.
A) hydrogen bonds
B) nonpolar covalent bonds
C) polar covalent bonds
D) ionic bonds
46) The partial negative charge at one end of a water molecule is attracted to the partial positive charge of another water molecule. What is this attraction called?
A) a covalent bond
B) a hydrogen bond
C) an ionic bond
D) a van der Waals interaction
47) The partial negative charge in a molecule of water occurs because _____.
A) the oxygen atom donates an electron to each of the hydrogen atoms
B) the electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen atom nucleus than around the hydrogen atom nucleus
C) the oxygen atom has two pairs of electrons in its valence shell that are not neutralized by hydrogen atoms
D) one of the hydrogen atoms donates an electron to the oxygen atom
48) Water molecules can form hydrogen bonds with _____.
A) compounds that have polar covalent bonds
C) oxygen gas (O2) molecules
D) chloride ions
49) Which of the following is a property of liquid water? Liquid water _____.
A) is less dense than ice
B) has a specific heat that is lower than that for most other substances
C) has a heat of vaporization that is higher than that for most other substances
D) is nonpolar
50) Which of the following can be attributed to water's high specific heat?
A) Oil and water do not mix well.
B) A lake heats up more slowly than the air around it.
C) Ice floats on water.
D) Sugar dissolves in hot tea faster than in iced tea.
51) The cities of Portland, Oregon, and Minneapolis, Minnesota, are at about the same latitude, but Minneapolis has much hotter summers and much colder winters than Portland. Why?
A) They are not at the same exact latitude.
B) The ocean near Portland moderates the temperature.
C) Fresh water is more likely to freeze than salt water.
D) Minneapolis is much windier, due to its location in the middle of North America.
52) 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. You have a reference book with tables listing the physical properties of many liquids. In choosing a coolant for your car, which table would you check first?
B) density at room temperature
C) heat of vaporization
D) specific heat
53) Water has many exceptional and useful properties. Which is the rarest property among compounds?
A) Water is a solvent.
B) Solid water is less dense than liquid water.
C) Water has a high heat capacity.
D) Water has surface tension.
54) Which of the following effects can occur because of the high surface tension of water?
A) Lakes cannot freeze solid in winter, despite low temperatures.
B) A raft spider can walk across the surface of a small pond.
C) Organisms can resist temperature changes, although they give off heat due to chemical reactions.
D) Sweat can evaporate from the skin, helping to keep people from overheating.
55) Which of the following takes place as an ice cube cools a drink?
A) Molecular collisions in the drink increase.
B) Kinetic energy in the liquid water decreases.
C) A calorie of heat energy is transferred from the ice to the water of the drink.
D) The specific heat of the water in the drink decreases.
56) Which type of bond must be broken for water to vaporize?
A) ionic bonds
B) polar covalent bonds
C) hydrogen bonds
D) both polar covalent bonds and hydrogen bonds
57) Why does ice float in liquid water?
A) The high surface tension of liquid water keeps the ice on top.
B) The ionic bonds between the molecules in ice prevent the ice from sinking.
C) Stable hydrogen bonds keep water molecules of ice farther apart than water molecules of liquid water.
D) The crystalline lattice of ice causes it to be denser than liquid water.
58) Hydrophobic substances such as vegetable oil are _____.
A) nonpolar substances that repel water molecules
B) nonpolar substances that have an attraction for water molecules
C) polar substances that repel water molecules
D) polar substances that have an affinity for water
59) Identical heat lamps are arranged to shine on two identical containers, one containing water and one methanol (wood alcohol), so that each liquid absorbs the same amount of energy minute by minute. The covalent bonds of methanol molecules are nonpolar, so there are no hydrogen bonds among methanol molecules. Which of the following graphs correctly describes what will happen to the temperature of the water and the methanol?
60) You have two beakers. One contains pure water, the other contains pure methanol (wood alcohol). The covalent bonds of methanol molecules are nonpolar, so there are no hydrogen bonds among methanol molecules. You pour crystals of table salt (NaCl) into each beaker. Predict what will happen.
A) Equal amounts of NaCl crystals will dissolve in both water and methanol.
B) NaCl crystals will not dissolve in either water or methanol.
C) NaCl crystals will dissolve readily in water but will not dissolve in methanol.
D) NaCl crystals will dissolve readily in methanol but will not dissolve in water.
61) Define a buffer and provide an example.
A buffer solution is one which resists changes in pH when small quantities of an acid or a base are added to it.
An acidic buffer solution is simply one which has a pH less than 7. Acidic buffer solutions are commonly made from a weak acid and one of its salts usually sodium salt. An example is carbonic acid + Na carbonate, the buffer which modulates the pH of blood.
A basic buffer solution is simply one which has a pH greater than 7. Basic buffer solutions are commonly made from a weak acid and one of its salts usually chloride salt. An example is ammonium hydroxide + ammonium chloride.
62) Consider the following reaction at equilibrium: What would be the effect of adding additional H2CO3?
A) It would drive the equilibrium dynamics to the right.
B) It would drive the equilibrium dynamics to the left.
C) Nothing would happen, because the reactants and products are in equilibrium.
D) The amounts of CO2 and H2O would decrease.
63) Which of the following statements is true about buffer solutions?
A) They maintain a constant pH when bases are added to them but not when acids are added to them.
B) They maintain a constant pH when acids are added to them but not when bases are added to them.
C) They fluctuate in pH when either acids or bases are added to them.
D) They maintain a relatively constant pH when either acids or bases are added to them.
64) Increased atmospheric CO2 concentrations might have what effect on seawater?
A) Seawater will become more alkaline, and carbonate concentrations will decrease.
B) There will be no change in the pH of seawater, because carbonate will turn to bicarbonate.
C) Seawater will become more acidic, and carbonate concentrations will decrease.
D) Seawater will become more acidic, and carbonate concentrations will increase.
65) How would acidification of seawater affect marine organisms? Acidification of seawater would _____.
A) increase dissolved carbonate concentrations and promote faster growth of corals and shell-building animals
B) decrease dissolved carbonate concentrations and promote faster growth of corals and shell-building animals
C) increase dissolved carbonate concentrations and hinder growth of corals and shell-building animals
D) decrease dissolved carbonate concentrations and hinder growth of corals and shell-building animals
66) If the cytoplasm of a cell is at pH 7, and the mitochondrial matrix is at pH 8, then the concentration of H+ ions _____.
A) is 10 times higher in the cytoplasm than in the mitochondrial matrix
B) is 10 times higher in the mitochondrial matrix than in the cytoplasm
C) in the cytoplasm is 7/8 the concentration in the mitochondrial matrix
D) in the cytoplasm is 8/7 the concentration in the mitochondrial matrix
67) The loss of water from a plant by transpiration cools the leaf. Movement of water in transpiration requires both adhesion to the conducting walls and wood fibers of the plant and cohesion of the molecules to each other. A scientist wanted to increase the rate of transpiration of a crop species to extend its range into warmer climates. The scientist substituted a nonpolar solution with an atomic mass similar to that of water for hydrating the plants. What do you expect the scientist’s data will indicate from this experiment?
A) The rate of transpiration will be the same for both water and the nonpolar substance.
B) The rate of transpiration will be slightly lower with the nonpolar substance as the plant will not have evolved with the nonpolar compound.
C) Transpiration rates will fall to zero as nonpolar compounds do not have the properties necessary for adhesion and cohesion.
D) Transpiration rates will increase as nonpolar compounds undergo adhesion and cohesion with wood fibers more readily than water.
68) In living systems molecules involved in hydrogen bonding almost always contain either oxygen or nitrogen or both. How do you explain this phenomenon?
A) Oxygen and nitrogen are elements found in both nucleic acids and proteins.
B) Oxygen and nitrogen are elements with very high attractions for their electrons.
C) Oxygen and nitrogen are elements found in fats and carbohydrates.
D) Oxygen and nitrogen were both components of gases that made up the early atmosphere on Earth.
13an 7. Acidic buffer solutions are commonly made from a weak acid and one of its salts usually sodium salt. An example is carbonic acid + Na carbonate, the buffer which modulates the pH of blood.
C) Seawater will become more acidic, and carb