Question 1

A pH of 7 is neutral due to the dissociation of water molecules in pure water.How many molecules of water have broken down into a hydroxide ion and a hydronium ion at pH 7?

Accepted Answer

A)  1 in 1 million
B)  1 in 10 million
C)  1 in 100 million
D)  1 in 1 billion B

Question 2

During chemical evolution,which of the following occurred in the molecules involved?

Accepted Answer

A)  Entropy decreased while potential energy increased.
B)  Entropy increased while potential energy increased.
C)  Entropy stayed constant while potential energy increased. A

Question 3

Why are some reactions exothermic?

Accepted Answer

A)  The products have lower potential energy than the reactants.
B)  They are spontaneous.
C)  They are nonspontaneous.
D)  The products have higher entropy (are more disordered) than the reactants. A

Question 4

A solution with a pH of 5 has how many more protons in it than a solution with a pH of 7?

Accepted Answer

A)  5 times
B)  10 times
C)  100 times
D)  1,000 times

Question 5

In the Gibbs free-energy relationship,why is the T term necessary?

Accepted Answer

A)  The free-energy change caused by a change in entropy is a function of temperature.
B)  The free-energy change caused by a change in potential energy is a function of temperature.
C)  The free-energy change caused by a change in electrical charge is a function of temperature.

Question 6

If an atom has a charge of +1,which of the following must be true?

Accepted Answer

A)  It has two more protons than neutrons.
B)  It has the same number of protons as electrons.
C)  It has one more electron than it has protons.
D)  It has one more proton than it has electrons.

Question 7

How many electrons are involved in a double covalent bond?

Accepted Answer

A)  one
B)  two
C)  three
D)  four

Question 8

When are atoms most stable?

Accepted Answer

A)  when they have the fewest possible valence electrons
B)  when they have the maximum number of unpaired electrons
C)  when all of the electron orbitals in the valence shell are filled
D)  when all electrons are paired

Question 9

Which of the following tends to make chemical reactions spontaneous?

Accepted Answer

A)  The reactants have lower potential energy than the products.
B)  The reactants are more ordered than the products.
C)  The temperature is low.
D)  The pressure is low.

Question 10

Which of the following is not a property of liquid water?

Accepted Answer

A)  Its density is greater than ice.
B)  Its specific heat is higher than that of most other substances.
C)  Its heat of vaporization is lower than that of most other substances.
D)  It is polar.

Question 11

How can you determine the approximate mass of an atom in atomic mass units?

Accepted Answer

A)  Add up the number of protons,electrons,and neutrons.
B)  Add up the number of protons and neutrons.
C)  Add up the number of protons and electrons.
D)  Take the number of protons minus the number of electrons.

Question 12

There are four elements that make up 95% of all matter found in organisms.Which of the following is not one of these?

Accepted Answer

A)  nitrogen
B)  calcium
C)  hydrogen
D)  oxygen

Question 13

Consider the following reaction at equilibrium: CO₂ + H₂O ↔ H₂CO₃.What would be the effect of adding additional H₂CO₃?

Accepted Answer

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.

Question 14

The Q10 rule states that,within their survivable range,the rates of biochemical processes of many ectothermic organisms approximately double with every 10-degree (C)rise in temperature.Why would this be true?

Accepted Answer

A)  Warmer molecules interact faster.
B)  There are more vibrational harmonics with greater temperature.
C)  Organisms move faster when they are warmer.
D)  Sunlight warms all organisms.

Question 15

How many electrons are involved in a triple covalent bond?

Accepted Answer

A)  two
B)  three
C)  six
D)  nine

Question 16

How many times can humans be sure the switch from nonlife to life has happened in the universe?

Accepted Answer

A)  once
B)  twice
C)  four times
D)  forty-two times

Question 17

If an atom has a charge of -2,which of the following must be true?

Accepted Answer

A)  It has two more electrons than protons.
B)  It has two more protons than electrons.
C)  It has two more protons than neutrons.
D)  It has two more neutrons than electrons.

Question 18

The difference between a polar covalent bond and an ionic bond is that electrons are shared unequally in a polar covalent bond,but are completely transferred (i.e.,not shared)in an ionic bond.

Accepted Answer

A)  true
B)  false

Question 19

Nitrogen (N)normally forms only three covalent bonds because it has a valence of five.However,ammonium has four covalent bonds,each to a different hydrogen (H)atom (H has a valence of one).Make a sketch of this molecule.Count the number of electrons in your sketch.Compare this number to the number of valence electrons in one N and four H's.What is the charge on this molecule most likely to be?

Accepted Answer

A)  +1
B)  -1
C)  +2
D)  -2

Question 20

While water has many exceptional and useful properties,which is the rarest property among compounds?

Accepted Answer

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.

Exam 2: Water and Carbon: the Chemical Basis of Life