Deck 2: Small Molecules and the Chemistry of Life

Question 1

Which of the following statements about covalent bonds is not true?

A) A covalent bond is stronger than a hydrogen bond.
B) A covalent bond can form between atoms of the same element.
C) Only a single covalent bond can form between two atoms.
D) A covalent bond results from the sharing of electrons by two atoms.
E) A covalent bond can form between atoms of different elements.

Answer 1

C

Question 2

When table salt (NaCl) is added to water,

A) a covalent bond is broken.
B) an acidic solution is formed.
C) the Na⁺ and Cl^- ions are separated.
D) the Na⁺ ions are attracted to the hydrogen atoms of water.
E) water molecules surround the Na⁺ (but not Cl^-) ions.

Answer 2

C

Question 3

Hydrophobic interactions

A) are stronger than hydrogen bonds.
B) are stronger than covalent bonds.
C) can hold two ions together.
D) can hold two nonpolar molecules together.
E) are responsible for the surface tension of water.

Answer 3

D

Question 4

The best reference source for the atomic number and mass number of elements is

A) a good chemistry text.
B) a dictionary.
C) the periodic table.
D) a general physics book.
E) a good biology text.

Question 5

An atom that is neutrally charged contains

A) only neutrons.
B) the same number of neutrons and electrons.
C) the same number of neutrons and protons.
D) the same number of protons and electrons.
E) no charged particles.

Question 6

The part of the atom that determines how the atom behaves chemically is the

A) proton.
B) electron.
C) neutron.
D) innermost shell.
E) nucleus.

Question 7

The hydrogen bond between two water molecules arises because water is

A) polar.
B) nonpolar.
C) a liquid.
D) small.
E) hydrophobic.

Question 8

The three most abundant elements in a human skin cell are

A) calcium, carbon, and oxygen.
B) carbon, hydrogen, and oxygen.
C) carbon, hydrogen, and sodium.
D) carbon, nitrogen, and potassium.
E) nitrogen, hydrogen, and argon.

Question 9

A human hair is found to have a high ratio of ¹⁸O to ¹⁶O. From this information it can be assumed that

A) the person is suffering from a chronic disease such as diabetes.
B) the person has experienced prolonged exposure to radioactivity.
C) the person lives in a region where "heavy" water is consumed.
D) the person regularly uses a protein-rich hair conditioner.
E) the person eats a diet high in cholesterol-rich meat.

Question 10

Which of the following statements about atoms is true?

A) The negative charge of an electron is larger than the positive charge of a proton. This is the reason that there are usually more protons than electrons in an atom.
B) Neutrons add mass to an atom without influencing other properties.
C) When the number of protons equals the number of electrons, an atom has a neutral charge.
D) Atoms of an element are radioactive whenever they vary in their number of neutrons.
E) The energy level of electrons is higher in shells close to the nucleus.

Question 11

The atomic weight (atomic mass) of an element

A) equals the number of neutrons in an atom.
B) equals the number of protons in an atom.
C) equals the number of electrons in an atom.
D) equals the number of neutrons plus the number of protons.
E) depends on the relative abundances of its electrons and neutrons.

Question 12

The compounds that sulfur forms with hydrogen are most like the compounds found in which of the following?

A) CH₄
B) NH₃
C) H₂O
D) NaCl
E) CaCl₂

Question 13

Which of the following statements about water is not true?

A) It releases a large amount of heat when changing from liquid into vapor.
B) Its solid form is less dense than its liquid form.
C) It is the most effective solvent for polar molecules.
D) It is typically the most abundant substance in a living organism.
E) It takes part in some important chemical reactions.

Question 14

Which component of an atom does not significantly add to its mass?

A) Proton
B) Neutron
C) Electron
D) Both a and b
E) All of the above

Question 15

The reaction HCl $\to$ H⁺ + Cl^- in the human stomach is an example of the

A) cleavage of a hydrophobic bond.
B) formation of a hydrogen bond.
C) elevation of the pH of the stomach.
D) formation of ions by dissolving an acid.
E) formation of polar covalent bonds.

Question 16

The number of protons in a neutral atom equals the number of

A) neutrons.
B) electrons.
C) electrons plus neutrons.
D) neutrons minus electrons.
E) isotopes.

Question 17

Which of the following statements about the isotopes of an element is not true?

A) They all have the same atomic number.
B) They all have the same number of protons.
C) They all have the same number of neutrons.
D) They all have the same number of electrons.
E) They all have identical chemical properties.

Question 18

Compared to carbon, silicon has the same number of

A) protons.
B) valence (outer-shell) electrons.
C) neutrons.
D) electrons.
E) Both a and c

Question 19

The atomic number of an element

A) equals the number of neutrons in an atom.
B) equals the number of protons in an atom.
C) equals the number of protons minus the number of neutrons.
D) equals the number of neutrons plus the number of protons.
E) depends on the isotope.

Question 20

What is the difference between an atom and an element?

A) An atom is made of protons, electrons, and sometimes neutrons; an element is a substance composed of only one kind of atom.
B) An element is made of protons, electrons, and sometimes neutrons; an atom is a substance composed of only one kind of element.
C) An atom does not contain electrons, whereas an element does.
D) An atom contains protons and electrons, whereas an element contains protons, electrons, and neutrons.
E) None of the above

Question 21

The ability of atoms to combine with other atoms is determined by

A) the atom's atomic weight.
B) the number and distribution of electrons.
C) the atom's ability to form isomers.
D) the atom's nucleus.
E) pH.

Question 22

The atomic number of an element is the same as the number of _______ in each atom.

A) neutrons
B) protons plus electrons
C) protons
D) neutrons plus protons
E) neutrons plus electrons

Question 23

The four elements most common in organisms are

A) calcium, iron, hydrogen, and oxygen.
B) water, carbon, hydrogen, and oxygen.
C) carbon, oxygen, hydrogen, and nitrogen.
D) nitrogen, carbon, iron, and hydrogen.
E) phosphorus, water, carbon, and oxygen.

Question 24

Which of the elements listed below does not follow the octet rule?

A) Sodium
B) Chlorine
C) Carbon
D) Hydrogen
E) Nitrogen

Question 25

Carbon-12 is the most abundant isotope of carbon on Earth. Carbon-13 makes up about 1 percent of Earth's carbon atoms, and is useful for radioimaging. Which of the following is true?

A) Carbon-13 has more protons than carbon-12.
B) Carbon-13 has more neutrons than carbon-12.
C) Carbon-13 has more electrons than carbon-12.
D) Carbon-13 has an electronic configuration that is different from that of carbon-12.
E) Carbon-13 has an equal number of protons and neutrons.

Question 26

Why is the atomic weight of hydrogen 1.008 and not exactly its mass number, 1.000?

A) Atomic weight does not take into account the weight of rare isotopes of an element.
B) Atomic weight is the average of the mass numbers of a representative sample of the element, including all its isotopes.
C) The atomic weight includes the weight of the electrons.
D) The atomic weight does not include the weight of the protons.
E) The mass number of an element is always lower than its atomic weight.

Question 27

Hydrogen, deuterium, and tritium all have the same

A) atomic weight.
B) atomic number.
C) mass.
D) density.
E) nuclear composition.

Question 28

Which of the following statements about the difference between ionic bonds and covalent bonds is true?

A) An ionic bond is stronger.
B) Electron sharing is more equal in the covalent bond.
C) An ionic bond occurs more often in aqueous solutions.
D) An ionic bond occurs only in acids.
E) A covalent bond occurs only in nonpolar molecules.

Question 29

An atom with _______ has an atomic mass of 14.

A) 14 neutrons
B) 14 electrons
C) 7 neutrons and 7 electrons
D) 7 protons and 7 electrons
E) 6 protons and 8 neutrons

Question 30

Which of the following elements is the most chemically reactive?

A) Hydrogen
B) Helium
C) Neon
D) Argon
E) They all have the same chemical reactivity.

Question 31

Nitrogen-14 and nitrogen-15 are isotopes. Nitrogen-15 is used to determine protein structure. Which of the following is true?

A) Nitrogen-15 has more protons than nitrogen-14.
B) Nitrogen-15 has more neutrons than nitrogen-14.
C) Nitrogen-15 has more electrons than nitrogen-14.
D) Nitrogen-15 has an electronic configuration that is different from that of nitrogen-14.
E) Nitrogen-15 has an equal number of protons and neutrons.

Question 32

An element has a weight of 131.3. The reason the number is not a whole number is that

A) the atomic weight includes the weight of electrons.
B) atomic weight is the average of the mass numbers of all the element's isotopes.
C) the neutrons do not have a single unit weight.
D) the atomic weight does not include the weight of protons.
E) the number of electrons may vary.

Question 33

Phosphorus has an atomic number of 15 and an atomic weight of 30.974. From this information it can be determined that this element

A) has isotopes.
B) forms isomers.
C) has a pH of 7.
D) is an ion.
E) is radioactive.

Question 34

³¹₁₅P and ³²₁₅P have virtually identical chemical and biological properties because they have the same

A) half-life.
B) number of neutrons.
C) atomic weight.
D) mass number.
E) number of electrons.

Question 35

Which of the following pairs has similar chemical properties?

A) ¹H and ²²Na
B) ¹²C and ²⁸Si
C) ¹⁶O and ⁸S
D) ¹²C and ¹⁴C
E) ⁸H and ²He

Question 36

Phosphorus has an atomic number of 15 and an atomic mass of 31. How many neutrons does phosphorus have?

A) 5
B) 16
C) 30
D) 31
E) 47

Question 37

The mass number of an atom is determined primarily by the _______ it contains.

A) number of electrons
B) number of protons
C) sum of the number of protons and electrons
D) sum of the number of protons and neutrons
E) number of charges

Question 38

Which of the following elements is contained by all living things?

A) Nitrogen
B) Phosphorus
C) Sulfur
D) Carbon
E) All of the above

Question 39

The atomic mass of an element is the same as the number of _______ in each atom.

A) electrons
B) protons
C) neutrons
D) protons plus neutrons
E) electrons plus neutrons

Question 40

Because atoms can have the same number of protons but a different number of neutrons, elements have

A) isotopes.
B) more than one atomic mass listed on the periodic table.
C) more than one atomic number.
D) various means of forming chemical bonds.
E) isomers.

Question 41

Chemical bonds formed by electrical attractions are

A) covalent bonds.
B) ionic bonds.
C) hydrogen bonds.
D) van der Waals forces.
E) Both b and c

Question 42

Which of the following is the correct order (in decreasing order) for the relative strengths of chemical bonds?

A) Covalent, ionic, hydrogen, van der Waals forces
B) Ionic, covalent, hydrogen, van der Waals forces
C) van der Waals forces, covalent, ionic, hydrogen
D) Hydrogen, covalent, van der Waals forces, ionic
E) Ionic, covalent, van der Waals forces, hydrogen

Question 43

Which of the following molecules is held together primarily by ionic bonds?

A) H₂O
B) C₆H₁₂O₆
C) NaCl
D) H₂
E) NH₃

Question 44

Cholesterol is composed primarily of carbon and hydrogen atoms. Therefore, one would expect cholesterol to be

A) insoluble in water.
B) a polar molecule.
C) a base.
D) an acid.
E) a buffer.

Question 45

Which of the following atoms usually has the greatest number of covalent bonds with other atoms?

A) Carbon
B) Oxygen
C) Sulfur
D) Hydrogen
E) Nitrogen

Question 46

A covalent bond is the sharing of _______ between atoms, whereas an ionic bond is the _______.

A) neutrons; sharing of electrons
B) electrons; electric attraction between two atoms
C) protons; electric attraction between two atoms
D) protons; sharing of electrons
E) electrons; transfer of electrons from one atom to another

Question 47

Ionic bonds are

A) attractions between oppositely charged ions.
B) the result of electron sharing.
C) the strongest of the chemical bonds.
D) caused by partial electrical charges.
E) dependent upon hydrophobic interactions.

Question 48

In a hydrogen molecule, the two atoms are held together by

A) hydrogen bonds.
B) a shared pair of electrons.
C) van der Waals forces.
D) ionic attractions.
E) gravity.

Question 49

Two carbon atoms held together in a double covalent bond share _______ electron(s).

A) one
B) two
C) four
D) six
E) eight

Question 50

In addition to covalent and ionic bonds, which of the following interactions are important in biological systems?

A) van der Waals interactions
B) Hydrogen bonds
C) Hydrophobic interactions
D) Both a and b
E) All of the above

Question 51

Particles having a net negative charge are called

A) electronegative.
B) cations.
C) anions.
D) acids.
E) bases.

Question 52

All of the following are nonpolar except

A) O₂.
B) N₂.
C) CH₄.
D) NaCl.
E) H₂.

Question 53

Two atoms are held together in four covalent bonds because of forces between the

A) electrons and protons.
B) electrons.
C) protons and neutrons.
D) protons.
E) electrons and neutrons.

Question 54

A single covalent chemical bond represents the sharing of how many electrons?

A) One
B) Two
C) Three
D) Four
E) Six

Question 55

What determines if a molecule is polar, nonpolar, or ionic?

A) The number of protons
B) The bond distances
C) The differences in the electronegativities of the atoms
D) The ionic charges
E) The distance of the electrons from the nucleus

Question 56

Hydrogen bonds

A) form between two hydrogen atoms.
B) form only between hydrogen and oxygen atoms within a molecule.
C) form between a strong electronegative atom and hydrogen.
D) involve a transfer of electrons.
E) are the strongest bonds because of their length.

Question 57

The hydrogen bond between two water molecules arises because water is

A) polar.
B) nonpolar.
C) a liquid.
D) a small molecule.
E) hydrophobic.

Question 58

A van der Waals interaction is an attraction between

A) variations in electron distributions in two adjacent nonpolar molecules.
B) the electrons of one molecule and the nucleus of the same molecule.
C) the electrons of one molecule and the electrons of a nearby molecule.
D) nonpolar molecules, due to the exclusion of water.
E) nonpolar molecules, because they are surrounded by water molecules.

Question 59

When magnesium (Mg) bonds with another element, you would expect that it would

A) gain two electrons from the other element.
B) share four electrons with the other element.
C) lose two electrons to the other element.
D) form a hydrogen bond.
E) gain six electrons from the other element.

Question 60

Oxygen forms _______ covalent bond(s), carbon forms _______, and hydrogen forms _______.

A) one; four; one
B) four; four; four
C) two; four; none
D) two; four; one
E) two; two; two

Question 61

Which characteristic of water contributes to the relatively constant temperatures of the oceans?

A) Water ionizes only slightly.
B) It takes a small amount of heat energy to raise the temperature of water.
C) Water can contain large amounts of salt.
D) Water has the ability to ionize readily.
E) It takes a large amount of heat energy to raise the temperature of water.

Question 62

How would you make 100 ml of an aqueous solution with a 0.25 M concentration of a compound that has a molecular weight of 200 daltons?

A) Add 0.25 grams of the compound to 100 ml of water.
B) Add 250 grams of the compound to 100 ml of water.
C) Take 250 grams of the compound and add water until the volume equals 100 ml.
D) Take 50 grams of the compound and add water until the volume equals 100 ml.
E) Take 5 grams of the compound and add water until the volume equals 100 ml.

Question 63

Ice is used in beverages primarily because

A) it is composed only of water.
B) it floats.
C) it dilutes the taste.
D) people like to chew it.
E) it absorbs a lot of heat when it melts.

Question 64

The difference between an acid and a base is that an acid _______, whereas a base _______.

A) undergoes a reversible reaction; does not
B) releases OH^- ions in solution; accepts OH^- ions
C) releases H⁺ ions in solution; releases OH^- ions
D) releases OH^- ions in solution; releases H⁺ ions
E) releases H⁺ ions in solution; accepts H⁺ ions

Question 65

A 1.0 M solution of HCl has a pH of

A) 1.0.
B) 7.0.
C) 14.0.
D) 11.2.
E) 14.

Question 66

When exposed to extreme heat, the human body relies on _______ to absorb excess calories of heat and maintain normal body temperature.

A) evaporation
B) condensation
C) respiration
D) transpiration
E) All of the above

Question 67

To determine the number of molecules in a teaspoon of sugar you have to know

A) the density of the sugar.
B) the weight of the sugar.
C) the molecular weight of the sugar.
D) Avogadro's number.
E) the weight and molecular weight of the sugar, and Avogadro's number.

Question 68

Of the following compounds containing ¹H, ¹²C, and ¹⁶O, the one with the greatest number of molecules in a sample with a mass of 2 grams would be

A) CO.
B) CO₂.
C) HCOOH.
D) C₂H₅OH.
E) C₆H₁₂O₆.

Question 69

Two characteristics of water make it different from most other compounds: Its solid state is _______ its liquid state and it takes up _______ heat to change to its gaseous state.

A) less dense than; large amounts of
B) more dense than; small amounts of
C) less dense than; small amounts of
D) more dense than; large amounts of
E) just as dense as; no

Question 70

If you place a paper towel in a dish of water, the water will move up the towel by capillary action because water

A) molecules ionize.
B) is a good solvent.
C) molecules have hydrophobic interactions.
D) can form hydrogen bonds.
E) takes up large amounts of heat when it vaporizes.

Question 71

The molecular weight of water is 18.0154. One mole of water weighs _______ grams.

A) 9
B) 18
C) 20
D) 36.031
E) 6.023 $\times$ 10²³

Question 72

Sweating is a useful cooling device for humans because water

A) takes up a great deal of heat in changing from its liquid state to its gaseous state.
B) takes up a great deal of heat in changing from its solid state to its liquid state.
C) can exist in three states at temperatures common on Earth.
D) is an outstanding solvent.
E) ionizes readily.

Question 73

Which of the following correctly states an unusual property of water?

A) Water will not react with other atoms.
B) Water's solid state is denser than its liquid state.
C) Energy is not required to change water from a solid to a liquid.
D) Little heat energy is needed to raise the temperature of water.
E) The hydrogen bonds between water molecules continually form and break.

Question 74

A substance with a pH of 6.0 contains

A) 10⁶ hydrogen ions.
B) 6¹⁰ hydrogen ions.
C) 6¹⁰ moles of hydrogen ions.
D) more OH^- than H⁺.
E) 10^-6 moles of hydrogen ions.

Question 75

Which contains more molecules, a mole of hydrogen or a mole of carbon?

A) A mole of carbon
B) A mole of hydrogen
C) Both contain the same number of molecules.
D) Inadequate information is provided.
E) It depends on atmospheric pressure.

Question 76

A basic solution contains

A) more OH^- ions than H⁺ ions.
B) more H⁺ ions than OH^- ions.
C) the same number of OH^- ions and H⁺ ions.
D) no OH^- ions.
E) None of the above

Question 77

Surface tension and capillary action occur in water because it

A) is wet.
B) is dense.
C) has hydrogen bonds.
D) is nonpolar.
E) has ionic bonds.

Question 78

H₂SO₄ can ionize to yield two H⁺ ions and one SO₄^2- ion. H₂SO₄ is therefore

A) molar.
B) a base.
C) a buffer.
D) a solution.
E) an acid.

Question 79

Ice floats because

A) the crystal takes up more space than the liquid.
B) substances expand when cooled.
C) heat is released and heat makes water expand.
D) hydrogen bonds must break.
E) heat is absorbed.

Question 80

When sodium hydroxide (NaOH) is added to water, it ionizes, releasing OH^- and Na⁺ ions. The resulting solution is

A) acidic.
B) basic.
C) neutral.
D) molar.
E) a buffer.