West Los Angeles College » Chemistry » Chem 221 - Biochemistry for Science Majors » Fall 2021

Chem 221 - Biochemistry for Science Majors » Fall 2021 » L2 Water Part 1 of 2

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Question #1

A compound contains hydroxyl groups as its predominant functional group. Which of the following statements is true concerning this compound?

A. It won't form hydrogen bonds with water

B. It lacks a hydrogen, so it acts as an acid

C. It should dissolve in water

D. It should dissolve in a nonpolar solvent

E. It is hydrophobic

Question #2

Which one of the following functional groups does not participate in hydrogen bonding?

A. Methyl

B. Hydroxyl

C. Carboxyl

D. Amido (amide)

E. Amino

Question #3

Which of the following alcohols would be most soluble in water?

A. octanol

B. butanol

C. ethanol

D. methanol

Question #4

With respect to hydrogen bonds,

A. they are what make peptide bonds

B. they are stronger than covalent bonds

C. they are stronger than disulfide bonds

D. water does not have to be involved

Question #5

A solution with pH = 5 is __________ than a solution with pH = 7.

A. 100 times more acidic

B. 10 times more acidic

C. 2 times more basic

D. 10 times more basic

Question #6

The lone pair electrons on oxygen in a H2O molecule

A. form covalent bonds in ice

B. carry a partial positive charge

C. are not important for the properties of water

D. carry a partial negative charge

Question #7

The dissociation constant of H2O at 25° C is

A. 10^14 M

B. 10^-14 M

C. 10^7 M

D. 10^-7 M

Question #8

Weak acids generally have pKa

A. values less than 1

B. been seldom found in living systems

C. that cannot be used to buffer

D. values greater than 2

Question #9

The three-dimensional structure of macromolecules is formed and maintained primarily through non-covalent interactions. Which one of the following is not considered a non-covalent interaction?

A. Ionic interactions

B. Hydrogen bonds

C. van der Waals interactions

D. Hydrophobic interactions

E. Carbon-carbon bonds

Question #10

Osmosis is movement of a:

A. charged solute molecule (ion) across a membrane

B. polar solute molecule across a membrane

C. water molecule across a membrane

D. gas molecule across a membrane

E. nonpolar solute molecule across a membrane

Question #11

A hydronium ion:

A. is the usual form of one of the dissociation products of water in solution

B. is a hydrated proton

C. has the structure H3O+

D. is a hydrated hydrogen ion

E. All of the above are true

Question #12

A hydride ion:

A. contains two protons and two electrons and is the anion of hydrogen

B. has the structure H-, is the anion of hydrogen, and contains one protons and two electrons

C. contains two protons and two electrons and has the structure H-

Question #13

The aqueous solution with the lowest pH is:

A. 1 M HCl

B. 1 M formic acid (pKa = 3.75)

C. 10–12 M NaOH

D. 1 M acetic acid (pKa = 4.86)

E. 2 M HCl

Question #14

Salt dissolves well in water as water molecules

A. surround the ions because of their charge but do not form hydrogen bonds

B. form hydrogen bonds with the positively and negatively charged ions

C. share electrons with the ions to make polar covalent bonds

D. make nonpolar covalent bonds with the positively charged ions only

Question #15

If an ion for which the cell membrane does not have a transport protein is injected into the blood in significant amounts, which of the following would occur?

A. The volume of the blood would decrease

B. Blood proteins would diffuse into the cells to compensate

C. The blood cells would shrivel due to osmotic movement of water out of the cell

D. The blood cells would swell and eventually burst

E. The speed of blood flow through the vessels would increase

Question #16

The pKa of acid A is 4.5 and the pKa of acid B is 7.2. Acid B is a stronger acid than A.

A. FALSE

B. TRUE

Question #17

For a weak acid, low pKa means high dissociation.

A. FALSE

B. TRUE

Question #18

When crystalline substances (salts) dissolve in water, they acquire greater freedom of motion, which decreases the entropy of the system.

A. FALSE

B. TRUE

Question #19

Adding an acid to pure water decreases the [OH-]

A. TRUE

B. FALSE

Question #20

Adding an acid to pure water decreases the [H3O+]

A. FALSE

B. TRUE

Question #21

If NaOH(s) is dissolved in water, increasing the [OH-], the [H+] must decrease.

A. TRUE

B. FALSE

Question #22

In any aqueous solution at 25 °C, no matter what it contains, the product of [H+] and [OH-] must always equal 1.0 x 10-7.

A. TRUE

B. FALSE

Question #23

Hydrogen ions (H+) formed in the dissociation of water are immediately hydrated to hydronium ions (H3O+).

A. FALSE

B. TRUE

Question #24

In a phospholipid bilayer, the hydrophilic heads are exposed to outside water molecules while the hydrophobic tails inside the bilayer.

A. FALSE

B. TRUE

Question #25

Each acid has a characteristic tendency to lose its proton in an aqueous solution. The weaker the acid, the greater its tendency to lose its proton.

A. FALSE

B. TRUE

Question #26

A molecule change its ionization state by gaining or losing a proton (H+).

A. FALSE

B. TRUE

Question #27

Acetic acid is a strong acid.

A. FALSE

B. TRUE

Question #28

Sodium hydroxide is a strong base.

A. TRUE

B. FALSE

Question #29

Acetic acid has has two pKas.

A. FALSE

B. TRUE

Question #30

Many biochemical molecules are either weak acids or weak bases.

A. TRUE

B. FALSE

Question #31

When you add an acid or a base to water, the product of [H+] and [OH-] changes.

A. TRUE

B. FALSE

Question #32

If the pKa of acid A is 2 and the pKa of acid B is 4, that means that

A. A is 100 weaker than B

B. A is 200 stronger than B

C. A is 100 stronger than B

Question #33

Sulfuric acid is a weak acid.

A. TRUE

B. FALSE

Question #34

The degree of ionization of water to hydrogen ions (H+) and hydroxide ions (OH-) is considered

A. small

B. large

Question #35

The ionization of water is irreversible

A. TRUE

B. FALSE

Question #36

Of the non covalent interactions, the strongest is

A. hydrophobic interactions

B. ionic bonding

C. hydrogen bonding

Question #37

Of the non covalent interactions, the weakest is

A. hydrophobic interactions

B. hydrogen bonding

C. ionic bonds

Question #38

A. FALSE

B. TRUE

Question #39

Water has a

A. trigonal planar geometry

B. linear geometry

C. tetrahedral geometry

D. it varies

Question #40

The total number of hydrogen bonds of a water molecule is

A. 3

B. 2

C. 2

D. 4

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