BIOL 1441 Lecture Final Exam UTA |
Actual study set | Questions and verified
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About 25 of the 92 natural elements are known to be essential to life. Which four of these 25 elements
make up approximately 96% of living matter? - ANSW-carbon, hydrogen, nitrogen, oxygen
Trace elements are those required by an organism in only minute quantities. Which of the following is a
trace element that is required by humans and other vertebrates, but not by other organisms such as
bacteria or plants? - ANSW-iodine
Which of the following statements is false?
A) Carbon, hydrogen, oxygen, and nitrogen are the most abundant elements of living matter.
B) Some trace elements are very abundant on Earth.
C) Virtually all organisms require the same elements in the same quantities.
D) Iron is an example of an element needed by all organisms.
E) Other than some trace elements, animals are mostly made up of the same elements as plants, in
similar proportions. - ANSW-C) Virtually all organisms require the same elements in the same quantities.
Why is each element unique and different from other elements in chemical properties? - ANSW-Each
element has a unique number of protons in its nucleus
Knowing just the atomic mass of an element allows inferences about which of the following? - ANSW-the
number of protons plus neutrons in the element
In what way are elements in the same column of the periodic table the same? - ANSW-They have the
same number of electrons in their valence shell.
Oxygen has an atomic number of 8 and a mass number of 16. Thus, what is the atomic mass of an
oxygen atom? - ANSW-approximately 16 daltons
Carbon-12 is the most common isotope of carbon, and has an atomic mass of 12 daltons. A mole of
carbon in naturally occurring coal, however, weighs slightly more than 12 grams. Why? - ANSW-Some
carbon atoms in nature have more neutrons.
The precise weight of a mole of some pure elements like silicon (Si) can vary slightly from the standard
atomic mass, or even from sample to sample. Why? - ANSW-The element may have multiple stable
isotopes, and the isotopic composition may vary from sample to sample.
One difference between carbon-12 ( ) is that carbon-14 ( ) has - ANSW-two more neutrons than carbon-
12.
An atom has 6 electrons in its outer shell. How many unpaired electrons does it have? - ANSW-2
The atomic number of nitrogen is 7. Nitrogen-15 is heavier than nitrogen-14 because the atomic nucleus
of nitrogen-15 contains how many neutrons? - ANSW-8
Electrons exist only at fixed levels of potential energy. However, if an atom absorbs sufficient energy, a
possible result is that - ANSW-an electron may move to an electron shell farther away from the nucleus.
From its atomic number of 15, it is possible to predict that the phosphorus atom has - ANSW-15 protons
and 15 electrons.
,The atomic number of each atom is given to the left of each of the elements below. Which of the atoms
has the same valence as carbon (12 6 C )? - ANSW-14Si silicon
Two atoms appear to have the same mass number. These atoms - ANSW-must have the same number of
protons + neutrons.
Fluorine has an atomic number of 9 and a mass number of 19. How many electrons are needed to
complete the valence shell of a fluorine atom? - ANSW-1
What is the maximum number of electrons in a single 2 p orbital of an atom? - ANSW-2
Phosphorus-32, a radioactive isotope of phosphorus-31 (atomic number 15), undergoes a form of
radioactive decay whereby a neutron turns into a proton and emits radiation in the form of an electron.
What is the product of such radioactive decay of phosphorus-32? - ANSW-sulfur-32 (atomic number 16)
An atom with atomic number 12 would have what type of chemical behavior in bonding with other
elements? - ANSW-It would form ions with a +2 charge.
If a salamander relied on hydrogen bonds to cling to surfaces, what type of surface would cause the
most problems for this animal? - ANSW-a surface made with carbon and hydrogen atoms covalently
bonded together
A covalent chemical bond is one in which - ANSW-outer-shell electrons of two atoms are shared so as to
satisfactorily fill the outer electron shells of both atoms.
What is the maximum number of covalent bonds an element with atomic number 8 can make? - ANSW-2
Nitrogen (N) is much more electronegative than hydrogen (H). Which of the following statements is
correct about the atoms in ammonia (NH3)?
A) Each hydrogen atom has a partial positive charge; the nitrogen atom has a partial negative charge.
B) The nitrogen atom has a strong positive charge; each hydrogen atom has a strong positive charge.
C) Each hydrogen atom has a slight negative charge; the nitrogen atom has a strong positive charge.
D) The nitrogen atom has a slight positive charge; each hydrogen atom has a slight negative charge.
E) There are covalent bonds between the hydrogen atoms and polar bonds between each hydrogen
atom and the nitrogen atom. - ANSW-A) Each hydrogen atom has a partial positive charge; the nitrogen
atom has a partial negative charge.
When two atoms are equally electronegative, they will interact to form - ANSW-nonpolar covalent
bonds.
What results from an unequal sharing of electrons between atoms? - ANSW-a polar covalent bond
A covalent bond is likely to be polar when - ANSW-one of the atoms sharing electrons is much more
electronegative than the other atom.
Which of the following molecules contains the most polar covalent bonds?
A) H2
B) O2
C) CO2
D) H2O
E) CH4 - ANSW-D) H2O
In ammonium chloride salt (NH4Cl) the anion is a single chloride ion, Cl. What is the cation of NH4Cl? -
ANSW-NH4, with a charge of +1
,Which of the following is true for this reaction?
3 H2 + N2 ↔ 2 NH3
A) The reaction is nonreversible.
B) Hydrogen and nitrogen are the reactants of the reverse reaction.
C) Hydrogen and nitrogen are the products of the forward reaction.
D) Ammonia is being formed and decomposed.
E) Hydrogen and nitrogen are being decomposed. - ANSW-D) Ammonia is being formed and decomposed
Describe chemical equilibrium - ANSW-Forward and reverse reactions continue with no effect on the
concentrations of the reactants and products.
In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by - ANSW-polar
covalent bonds.
The slight negative charge at one end of one water molecule is attracted to the slight positive charge of
another water molecule. What is this attraction called? - ANSW-a hydrogen bond
The partial negative charge in a molecule of water occurs because - ANSW-the electrons shared between
the oxygen and hydrogen atoms spend more time around the oxygen atom nucleus than around the
hydrogen atom nucleus.
Sulfur is in the same column of the periodic table as oxygen, but has electronegativity similar to carbon.
Compared to water molecules, molecules of H2S - ANSW-will not form hydrogen bonds with each other.
Water molecules are able to form hydrogen bonds with - ANSW-compounds that have polar covalent
bonds.
Which of the following effects is produced by the high surface tension of water? - ANSW-A water strider
can walk across the surface of a small pond.
Which of the following takes place as an ice cube cools a drink? - ANSW-Kinetic energy in the drink
decreases.
A dietary Calorie equals 1 kilocalorie. Which of the following statements correctly defines 1 kilocalorie? -
ANSW-1,000 calories, or the amount of heat required to raise the temperature of 1 kg of water by 1°C
Liquid water's high specific heat is mainly a consequence of the - ANSW-absorption of heat when
hydrogen bonds break.
Which type of bond must be broken for water to vaporize? - ANSW-hydrogen bonds
Temperature usually increases when water condenses. Which behavior of water is most directly
responsible for this phenomenon? - ANSW-the release of heat by the formation of hydrogen bonds
Why does evaporation of water from a surface cause cooling of the surface? - ANSW-The water
molecules with the most heat energy evaporate more readily.
Why does ice float in liquid water? - ANSW-Hydrogen bonds stabilize and keep the molecules of ice
farther apart than the water molecules of liquid water.
Hydrophobic substances such as vegetable oil are - ANSW-nonpolar substances that repel water
molecules.
One mole (mol) of glucose (molecular mass = 180 daltons) is - ANSW-both 180 grams of glucose and 6.02
× 1023 molecules of glucose.
, How many molecules of glucose (C6H12O6 molecular mass = 180 daltons) would be present in 90 grams
of glucose? - ANSW-(90/180) × 6.02 × 1023
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)? - ANSW-1 L of 1.0 M NaCl
The molecular weight of water is 18 daltons. What is the molarity of 1 liter of pure water? (Hint: What is
the mass of 1 liter of pure water?) - ANSW-55.6 M
1 liter of water weighs 1000g. 1M of water should have 18g of water, therefore 1000g of pure water
should have molarity of 1000/18 = 55.6.
You have a freshly prepared 1 M solution of glucose in water. You carefully pour out a 100 mL sample of
that solution. How many glucose molecules are included in that 100 mL sample? - ANSW-6.02 × 1022
Which of the following ionizes completely in solution and is considered to be a strong base (alkali)? -
ANSW-NaOH
A 0.01 M solution of a substance has a pH of 2. What can you conclude about this substance? - ANSW-It
is a strong acid that ionizes completely in water.
A given solution contains 0.0001(10-4) moles of hydrogen ions [H+] per liter. Which of the following best
describes this solution? - ANSW-acidic: will give H+ to weak acids, but accept H+ from strong acids
A solution contains 0.0000001(10-7) moles of hydroxyl ions [OH-] per liter. Which of the following best
describes this solution? - ANSW-neutral
What is the pH of a solution with a hydroxyl ion [OH-] concentration of 10-12 M? - ANSW-pH 2
Which of the following solutions would require the greatest amount of base to be added to bring the
solution to neutral pH?
A) gastric juice at pH 2
B) vinegar at pH 3
C) tomato juice at pH 4
D) black coffee at pH 5
E) household bleach at pH 12 - ANSW-gastric juice at pH 2
What is the hydrogen ion [H+] concentration of a solution of pH 8? - ANSW-10-8 M
If the pH of a solution is decreased from 9 to 8, it means that the - ANSW-concentration of H+ has
increased tenfold (10X) and the concentration of OH- has decreased to one-tenth (1/10) what they were
at pH 9.
If the pH of a solution is increased from pH 5 to pH 7, it means that the - ANSW-concentration of OH- is
100 times greater than what it was at pH 5.
One liter of a solution of pH 2 has how many more hydrogen ions (H+) than 1 L of a solution of pH 6? -
ANSW-10,000 times more
One liter of a solution of pH 9 has how many more hydroxyl ions (OH-) than 1 L of a solution of pH 4? -
ANSW-100,000 times more
Which of the following statements is true about buffer solutions? - ANSW-They maintain a relatively
constant pH when either acids or bases are added to them.
Actual study set | Questions and verified
study solutions
About 25 of the 92 natural elements are known to be essential to life. Which four of these 25 elements
make up approximately 96% of living matter? - ANSW-carbon, hydrogen, nitrogen, oxygen
Trace elements are those required by an organism in only minute quantities. Which of the following is a
trace element that is required by humans and other vertebrates, but not by other organisms such as
bacteria or plants? - ANSW-iodine
Which of the following statements is false?
A) Carbon, hydrogen, oxygen, and nitrogen are the most abundant elements of living matter.
B) Some trace elements are very abundant on Earth.
C) Virtually all organisms require the same elements in the same quantities.
D) Iron is an example of an element needed by all organisms.
E) Other than some trace elements, animals are mostly made up of the same elements as plants, in
similar proportions. - ANSW-C) Virtually all organisms require the same elements in the same quantities.
Why is each element unique and different from other elements in chemical properties? - ANSW-Each
element has a unique number of protons in its nucleus
Knowing just the atomic mass of an element allows inferences about which of the following? - ANSW-the
number of protons plus neutrons in the element
In what way are elements in the same column of the periodic table the same? - ANSW-They have the
same number of electrons in their valence shell.
Oxygen has an atomic number of 8 and a mass number of 16. Thus, what is the atomic mass of an
oxygen atom? - ANSW-approximately 16 daltons
Carbon-12 is the most common isotope of carbon, and has an atomic mass of 12 daltons. A mole of
carbon in naturally occurring coal, however, weighs slightly more than 12 grams. Why? - ANSW-Some
carbon atoms in nature have more neutrons.
The precise weight of a mole of some pure elements like silicon (Si) can vary slightly from the standard
atomic mass, or even from sample to sample. Why? - ANSW-The element may have multiple stable
isotopes, and the isotopic composition may vary from sample to sample.
One difference between carbon-12 ( ) is that carbon-14 ( ) has - ANSW-two more neutrons than carbon-
12.
An atom has 6 electrons in its outer shell. How many unpaired electrons does it have? - ANSW-2
The atomic number of nitrogen is 7. Nitrogen-15 is heavier than nitrogen-14 because the atomic nucleus
of nitrogen-15 contains how many neutrons? - ANSW-8
Electrons exist only at fixed levels of potential energy. However, if an atom absorbs sufficient energy, a
possible result is that - ANSW-an electron may move to an electron shell farther away from the nucleus.
From its atomic number of 15, it is possible to predict that the phosphorus atom has - ANSW-15 protons
and 15 electrons.
,The atomic number of each atom is given to the left of each of the elements below. Which of the atoms
has the same valence as carbon (12 6 C )? - ANSW-14Si silicon
Two atoms appear to have the same mass number. These atoms - ANSW-must have the same number of
protons + neutrons.
Fluorine has an atomic number of 9 and a mass number of 19. How many electrons are needed to
complete the valence shell of a fluorine atom? - ANSW-1
What is the maximum number of electrons in a single 2 p orbital of an atom? - ANSW-2
Phosphorus-32, a radioactive isotope of phosphorus-31 (atomic number 15), undergoes a form of
radioactive decay whereby a neutron turns into a proton and emits radiation in the form of an electron.
What is the product of such radioactive decay of phosphorus-32? - ANSW-sulfur-32 (atomic number 16)
An atom with atomic number 12 would have what type of chemical behavior in bonding with other
elements? - ANSW-It would form ions with a +2 charge.
If a salamander relied on hydrogen bonds to cling to surfaces, what type of surface would cause the
most problems for this animal? - ANSW-a surface made with carbon and hydrogen atoms covalently
bonded together
A covalent chemical bond is one in which - ANSW-outer-shell electrons of two atoms are shared so as to
satisfactorily fill the outer electron shells of both atoms.
What is the maximum number of covalent bonds an element with atomic number 8 can make? - ANSW-2
Nitrogen (N) is much more electronegative than hydrogen (H). Which of the following statements is
correct about the atoms in ammonia (NH3)?
A) Each hydrogen atom has a partial positive charge; the nitrogen atom has a partial negative charge.
B) The nitrogen atom has a strong positive charge; each hydrogen atom has a strong positive charge.
C) Each hydrogen atom has a slight negative charge; the nitrogen atom has a strong positive charge.
D) The nitrogen atom has a slight positive charge; each hydrogen atom has a slight negative charge.
E) There are covalent bonds between the hydrogen atoms and polar bonds between each hydrogen
atom and the nitrogen atom. - ANSW-A) Each hydrogen atom has a partial positive charge; the nitrogen
atom has a partial negative charge.
When two atoms are equally electronegative, they will interact to form - ANSW-nonpolar covalent
bonds.
What results from an unequal sharing of electrons between atoms? - ANSW-a polar covalent bond
A covalent bond is likely to be polar when - ANSW-one of the atoms sharing electrons is much more
electronegative than the other atom.
Which of the following molecules contains the most polar covalent bonds?
A) H2
B) O2
C) CO2
D) H2O
E) CH4 - ANSW-D) H2O
In ammonium chloride salt (NH4Cl) the anion is a single chloride ion, Cl. What is the cation of NH4Cl? -
ANSW-NH4, with a charge of +1
,Which of the following is true for this reaction?
3 H2 + N2 ↔ 2 NH3
A) The reaction is nonreversible.
B) Hydrogen and nitrogen are the reactants of the reverse reaction.
C) Hydrogen and nitrogen are the products of the forward reaction.
D) Ammonia is being formed and decomposed.
E) Hydrogen and nitrogen are being decomposed. - ANSW-D) Ammonia is being formed and decomposed
Describe chemical equilibrium - ANSW-Forward and reverse reactions continue with no effect on the
concentrations of the reactants and products.
In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by - ANSW-polar
covalent bonds.
The slight negative charge at one end of one water molecule is attracted to the slight positive charge of
another water molecule. What is this attraction called? - ANSW-a hydrogen bond
The partial negative charge in a molecule of water occurs because - ANSW-the electrons shared between
the oxygen and hydrogen atoms spend more time around the oxygen atom nucleus than around the
hydrogen atom nucleus.
Sulfur is in the same column of the periodic table as oxygen, but has electronegativity similar to carbon.
Compared to water molecules, molecules of H2S - ANSW-will not form hydrogen bonds with each other.
Water molecules are able to form hydrogen bonds with - ANSW-compounds that have polar covalent
bonds.
Which of the following effects is produced by the high surface tension of water? - ANSW-A water strider
can walk across the surface of a small pond.
Which of the following takes place as an ice cube cools a drink? - ANSW-Kinetic energy in the drink
decreases.
A dietary Calorie equals 1 kilocalorie. Which of the following statements correctly defines 1 kilocalorie? -
ANSW-1,000 calories, or the amount of heat required to raise the temperature of 1 kg of water by 1°C
Liquid water's high specific heat is mainly a consequence of the - ANSW-absorption of heat when
hydrogen bonds break.
Which type of bond must be broken for water to vaporize? - ANSW-hydrogen bonds
Temperature usually increases when water condenses. Which behavior of water is most directly
responsible for this phenomenon? - ANSW-the release of heat by the formation of hydrogen bonds
Why does evaporation of water from a surface cause cooling of the surface? - ANSW-The water
molecules with the most heat energy evaporate more readily.
Why does ice float in liquid water? - ANSW-Hydrogen bonds stabilize and keep the molecules of ice
farther apart than the water molecules of liquid water.
Hydrophobic substances such as vegetable oil are - ANSW-nonpolar substances that repel water
molecules.
One mole (mol) of glucose (molecular mass = 180 daltons) is - ANSW-both 180 grams of glucose and 6.02
× 1023 molecules of glucose.
, How many molecules of glucose (C6H12O6 molecular mass = 180 daltons) would be present in 90 grams
of glucose? - ANSW-(90/180) × 6.02 × 1023
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)? - ANSW-1 L of 1.0 M NaCl
The molecular weight of water is 18 daltons. What is the molarity of 1 liter of pure water? (Hint: What is
the mass of 1 liter of pure water?) - ANSW-55.6 M
1 liter of water weighs 1000g. 1M of water should have 18g of water, therefore 1000g of pure water
should have molarity of 1000/18 = 55.6.
You have a freshly prepared 1 M solution of glucose in water. You carefully pour out a 100 mL sample of
that solution. How many glucose molecules are included in that 100 mL sample? - ANSW-6.02 × 1022
Which of the following ionizes completely in solution and is considered to be a strong base (alkali)? -
ANSW-NaOH
A 0.01 M solution of a substance has a pH of 2. What can you conclude about this substance? - ANSW-It
is a strong acid that ionizes completely in water.
A given solution contains 0.0001(10-4) moles of hydrogen ions [H+] per liter. Which of the following best
describes this solution? - ANSW-acidic: will give H+ to weak acids, but accept H+ from strong acids
A solution contains 0.0000001(10-7) moles of hydroxyl ions [OH-] per liter. Which of the following best
describes this solution? - ANSW-neutral
What is the pH of a solution with a hydroxyl ion [OH-] concentration of 10-12 M? - ANSW-pH 2
Which of the following solutions would require the greatest amount of base to be added to bring the
solution to neutral pH?
A) gastric juice at pH 2
B) vinegar at pH 3
C) tomato juice at pH 4
D) black coffee at pH 5
E) household bleach at pH 12 - ANSW-gastric juice at pH 2
What is the hydrogen ion [H+] concentration of a solution of pH 8? - ANSW-10-8 M
If the pH of a solution is decreased from 9 to 8, it means that the - ANSW-concentration of H+ has
increased tenfold (10X) and the concentration of OH- has decreased to one-tenth (1/10) what they were
at pH 9.
If the pH of a solution is increased from pH 5 to pH 7, it means that the - ANSW-concentration of OH- is
100 times greater than what it was at pH 5.
One liter of a solution of pH 2 has how many more hydrogen ions (H+) than 1 L of a solution of pH 6? -
ANSW-10,000 times more
One liter of a solution of pH 9 has how many more hydroxyl ions (OH-) than 1 L of a solution of pH 4? -
ANSW-100,000 times more
Which of the following statements is true about buffer solutions? - ANSW-They maintain a relatively
constant pH when either acids or bases are added to them.
