Deck 1: Nature of Molecules

Question 1

When electrons in excited orbitals lose energy, that energy can

A) be used to drive another chemical process.
B) emit light.
C) be passed on to a neighbouring atom.
D) All of the answers are correct.
E) be used to drive photosynthesis in a leaf cell in sunlight.

Answer 1

All of the answers are correct.

Question 2

An oxygen atom has 8 protons, 8 neutrons and 8 electrons.

A) Its atomic number is 16.
B) Its mass number is 8.
C) It has 4 electrons in the first energy level (electron shell).
D) It has 6 electrons in the outermost energy level (electron shell).
E) It has 8 electrons in the outermost energy level (electron shell).

Answer 2

It has 6 electrons in the outermost energy level (electron shell).

Question 3

Atoms of the same element can exist in different forms called isotopes. The most common isotope of carbon is carbon-12 but it has two less-common isotopes, carbon-13 and carbon-14. The less-common isotopes have

A) the same number of electrons but more protons.
B) the same number of protons but more neutrons.
C) the same number of neutrons but more protons.
D) the same number of protons but more electrons.
E) the same number of neutrons but more electrons.

Answer 3

the same number of protons but more neutrons.

Question 4

Ionic bonds are formed by the

A) attraction between atoms with opposite polarity.
B) transfer of electrons from one atom to another.
C) sharing of electrons between oppositely charged ions.
D) attraction between positively and negatively charged ions of the same element.
E) sharing of electrons in the outer electron orbital of an atom.

Question 5

Hydrogen bonds can form between

A) carbon and hydrogen atoms.
B) oxygen and hydrogen atoms in the same water molecule.
C) oxygen and hydrogen atoms in adjacent molecules.
D) hydrogen atoms in adjacent molecules.
E) hydrogen atoms within the same molecule.

Question 6

One of the properties that make water an ideal medium for living organisms is that water

A) can absorb considerable amounts of heat with little change in temperature.
B) expands and becomes more dense as it changes from solid to liquid form.
C) releases heat when it evaporates.
D) is a universal solvent.
E) has a high boiling point.

Question 7

Hydrogen bonding between water molecules gives water a high level of structural organisation. In ice, the maximum number of hydrogen bonds formed with one water molecule is

A) 2.
B) 3.
C) 4.
D) 6.
E) 1.

Question 8

Water is a versatile solvent because water molecules are

A) small.
B) polar.
C) hydrophilic.
D) loosely connected by hydrogen bonds.
E) hydrophobic.

Question 9

Which of the following statements is CORRECT?

A) The internal pH of the cells of an organism is usually the same as the pH of the external environment.
B) The internal pH of the cells of an organism may be quite different to the pH of the external environment.
C) Regardless of the internal pH of their cells, most living organisms can only survive within a narrow range of environmental pH.
D) Regardless of the pH of the environment, most living organisms will not survive if the internal pH of their cells fluctuates.
E) The internal pH of a muscle cell may become more basic during exercise.

Question 10

The interior of a lysosome in an animal cell has a pH of 5, while the cytosol of the cell has a pH of 7.4. This indicates that in comparison to the cytosol, the interior of the lysosome has a

A) lower concentration of total dissolved ions.
B) lower concentration of hydrogen ions.
C) higher concentration of bicarbonate ions.
D) higher concentration of hydrogen ions.
E) higher concentration of hydroxyl ions.

Question 11

Buffers are substances that assist cells and organisms to resist changes in pH by

A) accepting H⁺ ions as pH rises and releasing H⁺ ions as pH falls.
B) accepting OH^- ions as pH rises and releasing H⁺ ions as pH falls.
C) accepting H⁺ ions as pH falls and releasing H⁺ ions as pH rises.
D) accepting OH^- ions as pH falls and releasing H⁺ ions as pH rises.
E) accepting OH^- ions as pH falls and releasing OH^- ions as pH rises.

Question 12

Living organisms are composed of elements made of small units called

A) atoms.
B) protons.
C) neutrons.
D) electrons.
E) ions.

Question 13

Electrons exist as orbitals around the nucleus of an atom. Any orbital may contain

A) only 2 electrons.
B) 4 electrons.
C) 6 electrons.
D) 8 electrons.
E) any number of electrons depending on the orbital.

Question 14

The energy levels of electrons in their orbitals are determined by

A) the distance of the orbital from the nucleus.
B) the number of electrons in the orbital.
C) the number of neutrons in the nucleus.
D) the number of protons in the orbital.
E) the distance of the electrons in the orbital from each other.

Question 15

An element is a substance made up of

A) one type of atom only.
B) one type of molecule only.
C) at least two different types of atoms.
D) one atom linked to a different atom by a covalent bond.
E) an atom with one neutron and one proton in the nucleus.

Question 16

The small, negatively charged particles in an atom are called

A) electrons.
B) protons.
C) neutrons.
D) ions.
E) isotopes.

Question 17

The mass number of an atom is the number of

A) protons in the nucleus of an atom.
B) protons and neutrons combined in the nucleus of an atom.
C) neutrons in the nucleus of an atom.
D) electrons in an atom.
E) protons and electrons combined in an atom.

Question 18

Living organisms are composed predominantly of which of the following groups of elements:

A) Hydrogen (H); oxygen (O); carbon (C).
B) Hydrogen (H); oxygen (O); phosphorus (P).
C) Hydrogen (H); phosphorus (P); carbon (C).
D) Hydrogen (H); sodium (Na); chloride (Cl).
E) Oxygen (O); sodium (Na); chloride (Cl).

Question 19

The chemical properties of elements are determined primarily by

A) the number and arrangement of electrons in the highest energy level of the atom (the outermost electron shell).
B) the number of neutrons in the nucleus.
C) the number and arrangement of electrons in the lowest energy level of the atom (the innermost electron shell).
D) the ability of the electrons to change to a different orbital.
E) the type of bonds formed in the electron orbitals.

Question 20

Elements in living organisms are

A) similar to those found generally in the biosphere.
B) not similar to those found in the biosphere.
C) mainly carbon (C) and sodium chloride (NaCl).
D) highly reactive.
E) mostly atoms with a high atomic mass.

Question 21

Carbon has 4 electrons in its outer shell available for covalent bonding. Which of the following statements about carbon is INCORRECT?

A) Carbon is able to share the electrons with 4 atoms of hydrogen.
B) Carbon is able to share the electrons with other carbon atoms to form biomolecules.
C) Carbon is able to share electrons with oxygen to form carbon dioxide.
D) Carbon is able to form stable molecules by gaining 4 electrons in its outer electron orbital.
E) Carbon is able to form highly reactive molecules by losing 2 of the 4 electrons in its outer electron orbital.

Question 22

Nitrogen has 5 electrons in its outer orbital which allows it to share its electrons with

A) 2 hydrogen atoms.
B) 3 hydrogen atoms.
C) 4 hydrogen atoms.
D) 5 hydrogen atoms.
E) 6 hydrogen atoms.

Question 23

The pH of blood is 7.4. The pH of vinegar is 1.4. The blood sample has

A) 6 times lower [H⁺] than the vinegar.
B) 6,000 times higher [H⁺] than the vinegar.
C) 6,000 times lower [H⁺] than the vinegar.
D) 5.3 times lower [H⁺] than the vinegar.
E) a million times lower [H⁺] than the vinegar.

Question 24

When two atoms share a pair of electrons, the type of bonding is termed

A) ionic.
B) hydrogen.
C) covalent.
D) non-covalent.
E) unstable.

Question 25

When atoms gain or lose electrons from their orbital and so become charged, they are called

A) unstable.
B) non-covalent.
C) isotopes.
D) radioactive.
E) ions.

Question 26

In a molecule of water, the electrons are not equally shared between the atoms. This makes the molecule polar, and interaction with other polar molecules allows the formation of

A) covalent bonds.
B) van der Waals interactions.
C) hydrogen bonds.
D) ionic bonds.
E) stable bonds.

Question 27

Which of the following statements about chemical bonds is CORRECT?

A) Van der Waals forces allow temporary associations between molecules but the bonds are 100 times weaker than covalent bonds.
B) Covalent bonds involve the attraction between two ions of opposite charge.
C) Hydrogen bonds formed between hydrogen and oxygen atoms are strong, stable bonds.
D) In a molecule of water, the electrons are shared equally between the hydrogen and the oxygen molecule. This is the reason for the stability of water.
E) Ionic compounds result from the attraction between anions (positively charged ions) and cations (negatively charged ions).

Question 28

Water molecules tend to stick to other water molecules. This is known as

A) cohesion.
B) adhesion.
C) ionic bonding.
D) covalent bonding.
E) van der Waals forces.

Question 29

Which of the following statements about water is INCORRECT?

A) Water molecules tend to stick to one another (cohesion) and to other molecules that have charged surface groups to which water can hydrogen bond (adhesion).
B) The cohesive forces between water molecules are stronger between water molecules than between water and air molecules. This results in surface tension.
C) Both cohesive and adhesive forces are together responsible for the capillary action of water.
D) Only adhesive forces are responsible for the capillary action that causes water to rise through plant stems.
E) Heat is liberated when liquid water is turned to ice. This property of water is called the heat of fusion.

Question 30

Water is extremely important in all living things because of its properties. Which of the following is not a property of water?

A) Water is a polar molecule because of the unequal sharing of the electrons between hydrogen and oxygen.
B) Water molecules form hydrogen bonds with each other and with other polar molecules.
C) Hydrogen bonding makes water molecules cohesive. This cohesiveness results in surface tension.
D) Water repels non-polar molecules.
E) Water is an excellent buffer and maintains the intracellular pH in a cell.

Question 31

Compared with a pH of 7, a solution with a pH of 9 has

A) 2 times higher [H⁺] concentration.
B) 2 times lower [H⁺] concentration.
C) 1/100 the [H⁺] concentration.
D) 100 times the [H⁺] concentration.
E) 20 times lower [H⁺] concentration.

Question 32

Substances that release hydrogen ions (H⁺) into solution are

A) acids.
B) bases.
C) buffers.
D) hydrophobic.
E) carbon containing molecules.

Question 33

Which of the following statements is INCORRECT?

A) A buffer solution maintains a relatively constant pH either by removing hydrogen ions or by releasing them.
B) Water molecules ionise and dissociate forming both hydrogen (H⁺) and hydroxyl ions (OH^-).
C) The pH is the concentration of hydrogen ions in the solution.
D) The pH is the concentration of hydroxyl ions in the solution.
E) The pH scale is logarithmic.

Question 34

When a negatively charged electron is provided with more energy it can

A) Occupy space between orbitals.
B) Move to an outer orbital from an inner orbital.
C) Move closer to the positively charged nucleus.
D) Become a positron.
E) Bind to another electron in the same orbital.

Question 35

Why is Nitrogen fixation an energy intensive process?

A) NH₃ synthesis contains a rate-limiting step in its production.
B) Atmospheric N contains long Carbon chains that are difficult to break down.
C) N-fixation is a recently evolved mechanism and therefore inefficient.
D) Atmospheric N contains several single and double bonds.
E) Atmospheric N is bound by a triple covalent bond.

Question 36

In regard to non-covalent bonds, which statement is true?

A) Ionic bonds are weaker than covalent bonds.
B) Non-covalent bonds are important in maintaining the three-dimensional shape of proteins.
C) All statements are correct.
D) A Hydrogen bond is a non-covalent bond.
E) Non-covalent bonds are involved in the molecular role of inheritance.

Question 37

Hydrogen bonds

A) are stable in the interior of a double helix.
B) are weaker than van der Waals bonds.
C) between water molecules are transient.
D) are stronger than ionic bonds.
E) are not involved in the process of hereditary.

Question 38

In regard to chemical bonding, what is the order of bond strength from weakest to strongest?

A) Van der Waals, Hydrogen, Ionic, Covalent
B) Covalent, Ionic, Hydrogen, van der Waals
C) Hydrogen, Covalent, Ionic, van der Waals
D) Van der Waals, Ionic, Hydrogen, Covalent
E) Ionic, Hydrogen, van der Waals, Covalent

Question 39

Why does sucrose dissolve readily in water?

A) Because water molecules form H-bonds with the hydroxyl groups in sucrose.
B) Because sucrose is non-polar.
C) Because sucrose molecules are unable to form H-bonds with water molecules.
D) Because sucrose is an efficient solvent.
E) Because sucrose is hydrophobic.

Question 40

Like carbon, silicon can form complex molecules yet silicon-based life has not been found. Why not?

A) Carbon preferentially displaces silicon in extensive polymers.
B) Silicon atoms are not present in the lithosphere at high enough concentrations.
C) The covalent bonds between silicon atoms yield less energy when oxidised.
D) The oxide of silicon is a liquid.
E) Silicon is not a tetravalent atom.

Question 41

Which of the following atoms is NOT among those most commonly found to bind to carbon?

A) Oxygen.
B) Hydrogen.
C) Sulfur.
D) Potassium.
E) Nitrogen.

Question 42

Why is water a liquid over a wider range of temperatures than any other comparable solvent?

A) Because it is an efficient solute.
B) Because of its tetravalency.
C) Because of its hydrogen-bonding characteristics.
D) Because it can carry nutrients and oxygen in solution.
E) Because of its ability to form complex polymers.