BMB 212 exam 1

What type of bonds do you find within a water molecule?

polar covalent

Which of the following compounds are capable of hydrogen bonding with like molecules? Choose all that apply.

 

CH₃CH₂CH₂CH₂CH₃

 

CH₃CH₂OCH₂CH₃

 

CH₃NH₂

 

HOCH₂CH₂OH

CH₃NH_2, HOCH₂CH₂OH

Which of the following molecules is hydrophobic?

 

Sodium chloride

 

Ethyl alcohol

 

Hexane

 

Sucrose

 

Ammonia

hexane

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?

hydrogen bond

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)?

 

1 L of 0.5 M NaCl

 

1 L of 0.5 M glucose

 

1 L of 1.0 M NaCl

Correct

 

1 L of 1.0 M glucose

 

1 L of 1.0 M NaCl and 1 L of 1.0 M glucose will contain equal numbers of solute particles.

1 L of 1.0 M NaCl

Which of the following ionizes completely in solution and is considered to be a strong base (alkali)?

 

NaCl

 

HCl

 

NH₃

 

H₂CO₃

 

NaOH

NaOH

You have two beakers. One contains pure water, the other contains pure methanol (wood alcohol). The covalent bonds of methanol molecules are nonpolar, so there are no hydrogen bonds among methanol molecules. You pour crystals of table salt (NaCl) into each beaker. Predict what will happen.

NaCl crystals will dissolve readily in water but will not dissolve in methanol.

What type of bonds are formed between water molecules?

hydrogen bonds

Which of the following compounds is amphipathic?

 

H₂O

 

 CH₃CH₂CH₂CH₂CH₃

 

 HOOCCOOH

 

CH₃CH₂CH₂CH₂COOH

 

Both A and D are correct

CH₃CH₂CH₂CH₂COOH

Which of the following statements is true of weak acids dissolved in water?

 

They are completely ionized in water

 

They are totally unionized in water

 

They are partially ionized in water

 

The dissociation constant is a function of pH

 

The dissociation constant is a function of solute concentration

They are partially ionized in water

The major chemical elements in living things are:

carbon, hydrogen, nitrogen, oxygen, phosphorus, sulfur

Cell membranes are mostly made of this macromolecule, which keeps them from dissolving in water.

lipids

Carbohydrates contain/are made of units known as

monosaccharides

Notable features of eukaryotes include all of the following except ________.

 

Rapid cell division

 

Larger size

 

A complex internal structure

 

An endomembrane system

 

Organelles

Rapid cell division

Enzymes are a type of protein that speed up chemical reactions in living things. They are known as...

 

biological catalysts

 

carbohydrates

 

catalytic converters

 

Avogadro's number

biological catalysts

The partial negative charge in a molecule of water occurs because

 

the oxygen atom acquires an additional electron.

 

the electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen atom than around the hydrogen atom

 

the oxygen atom has two pairs of electrons in its valence shell that are not neutralized by hydrogen atoms.

 

the oxygen atom forms hybrid orbitals that distribute electrons unequally around the oxygen nucleus.

 

one of the hydrogen atoms donates an electron to the oxygen atom.

the electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen atom than around the hydrogen atom

What is the hydrogen ion concentration in a solution at pH 8.3?

 

5.0 × 10 ^−9 M

 

5.0 × 10 ^−8 M

 

0.5 M

 

5 M

5.0 × 10 ^−9 M

What would be the pH of 1L of water if 1 ml of 1M HCl is added?

 

3

 

0

 

2

 

13

3

What is the hydrogen ion [H⁺] concentration of a solution of pH 8?

10^-8 M

What is the pH of a 1 millimolar NaOH solution?

 

pH 3

 

pH 8

 

pH 9

 

pH 10

 

pH 11

11

What is the pH of a solution with a hydroxyl ion [OH^-] concentration of 10^-12 M?

 

pH 2

 

pH 4

 

pH 10

 

pH 12

 

pH 14

pH 2

If the pH of a solution is decreased from 9 to 8, it means that the

 

concentration of H+ has decreased to one-tenth (1/10) what it was at pH 9.

 

concentration of H+ has increased 10-fold (10X) compared to what it was at pH 9.

 

concentration of OH- has increased 10-fold (10X) compared to what it was at pH 9.

 

concentration of OH- has decreased to one-tenth (1/10) what it was at pH 9.

 

Both B and D are correct.

Both B and D are correct

If the pH of a solution is increased from pH 5 to pH 7, it means that the

 

concentration of H+ is twice (2X) what it was at pH 5.

 

concentration of H+ is half (1/2) what it was at pH 5.

 

concentration of OH- is 100 times greater than what it was at pH 5

 

concentration of OH- is one-hundredth (0.01X) what it was at pH 5.

 

concentration of H+ is 100 times greater and the concentration of OH- is one-hundredth what they were at pH 5.

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?

 

4 times more

 

400 times more

 

4,000 times more

 

10,000 times more

 

100,000 times more

10,000 times more

One liter of a solution pH 9 has how many more hydroxyl ions (OH^-) than 1 L of a solution of pH 4?

 

5 times more

 

100 times more

 

1,000 times more

 

10,000 times more

 

100,000 times more

100,000 times more

What is the pH of a solution with a hydrogen ion [H+] concentration of 10^-8 M?

 

pH 2

 

pH 4

 

pH 6

 

pH 8

 

pH 10

pH 8

this is the conjugate acid of what

bicarbonate ion

Which of the following would not form a suitable buffer?

 

Acetic acid/ acetate

 

Carbonic acid/ bicarbonate

 

Bicarbonate/ carbonate

 

Hydrochloric acid/ chloride

 

Phosphoric acid/ dihydrogen phosphate

The most important buffer in blood is __________.

 

Carbonate/bicarbonate buffer

 

Protein buffer

 

Phosphate buffer

 

Lactate buffer

 

Tartrate buffer

Carbonate/bicarbonate buffer

When an individual breathes very rapidly, large amounts of carbon dioxide are exhaled. What effect does this have on blood pH?

 

Acidosis

 

Alkalosis

 

No change

 

First acidosis then rebounding alkalosis

 

First alkalosis then rebounding acidosos

Alkalosis

Which of the following molecules are weak acids?

 

HCl

 

CO₃⁻²

 

HNO₃

 

HCO₃⁻

 

Both B and D

Which of the following species would form a buffer with HPO₄⁻²?

 

H₃PO₄

 

H₂PO₄⁻¹

 

CO₃⁻²

 

All would form buffers with HPO₄⁻²

 

Both A and B

H₂PO₄⁻¹

Which of the following species can form a buffer system?

 

Hydrochloric acid / Acetic acid

 

Acetic acid / Sodium chloride

 

Acetic acid / Ammonium chloride

 

Acetic acid/ Sodium acetate

 

Phosphoric acid / Sodium phosphate

Acetic acid/ Sodium acetate

Is it possible to prepare a buffer consisting of only carbonic acid and sodium carbonate?

no

Buffers are substances that help resist shifts in pH by

 

releasing H+ in acidic solutions.

 

donating H+ to a solution when they have been depleted.

 

releasing OH- in basic solutions.

 

accepting H+ when they are in excess.

donating H+ to a solution when they have been depleted, accepting H+ when they are in excess

One of the buffers that contribute to pH stability in human blood is carbonic acid (H2CO3). Carbonic acid is a weak acid that dissociates into a bicarbonate ion (HCO3-) and a hydrogen ion (H+). Thus,

H2CO3 <--> HCO3- + H+

If the pH of the blood drops, one would expect that the system would compensate for it by causing the: 

 

a decrease in the concentration of H2CO3 and an increase in the concentration of HCO3-.

 

the concentration of hydroxide ion (OH-) to increase.

 

the concentration of bicarbonate ion (HCO3-) to increase.

 

the HCO3- to act as a base and remove excess H+ with the formation of H2CO3.

the HCO3- to act as an acid and remove excess H+ with the formation of H2CO3.

the HCO3- to act as a base and remove excess H+ with the formation of H2CO3.

One of the buffers that contribute to pH stability in human blood is carbonic acid H₂CO₃. Carbonic acid is a weak acid that when placed in an aqueous solution dissociates into a bicarbonate ion (HCO₃^-) and a hydrogen ion (H⁺). Thus,

H₂CO₃ --> HCO₃^- + H⁺

If the pH of the blood increases, one would expect the system to compensate by 

(Hint: Think in terms of protons generated due to increase in pH. How would they shift the equilibrium)

 

a decrease in the concentration of H2CO3 and an increase in the concentration of H2O.

 

an increase in the concentration of H2CO3 and a decrease in the concentration of H2O.

 

a decrease in the concentration of HCO3- and an increase in the concentration of H2O.

 

an increase in the concentration of HCO3- and a decrease in the concentration of H2O.

 

a decrease in the concentration of HCO3- and an increase in the concentration of both H2CO3 and H2O.

a decrease in the concentration of H2CO3 and an increase in the concentration of H2O

The dissociation constant for an acid is 1 × 10−⁶. What is its pK_a?

 

0.6

 

-6

 

-0.6

 

6

6

A buffer solution at pH 10 has a ratio of [HA]/[A−] of 10. What is the pK_a of the acid?

 

8

 

9

 

10

 

11

 

12

11

Calculate the ratio of dihydrogen phosphate to hydrogen phosphate in blood at a pH 7.4. The K_a is 6.3 × 10⁻⁸.

 

1:1.6

 

1.4:1

 

1.6:1

 

1:1

1.6:1

The two sets of macromolecules most responsible for energy use in living things. 

 

Proteins

 

Carbohydrates

 

Nucleic acids

 

Lipids

carbs, lipids

Sugar is a macromolecule that falls under which group?

 

Proteins

 

Lipids

 

Nucleic acids

 

Carbohydrates

Carbohydrates

Cell membranes are mostly made of this macromolecule, which keeps them from dissolving in water.

 

Proteins

 

Lipids

 

Carbohydrates

 

Nucleic acids

Lipids

Enzymes are a type of protein that speed up chemical reactions in living things. They are known as...

 

carbohydrates

 

Avogadro's number

 

biological catalysts

 

catalytic converters

 

biological catalysts

We have long-term energy even if we don't eat for a period of time because of  

 

chemical bonds

 

enzymes

 

nucleic acids

 

proteins

 

lipids

lipids

Which of the following would be classified as a lipid?

 

starch—a polysaccharide

 

catalase—an enzyme

 

cholesterol—a steroid

 

alanine—an amino acid

cholesterol

The following molecule is an example of which single class of compounds?

CH₃CH₂CH(NH₂)COOH

 

Amino acid

 

Amine

 

Acid

 

Alcohol

 

Ester

Amino acid

The following molecule is an example of which class of compounds?

CH₃CH₂CH₂COOCH₂CH₃

 

Aldehyde

 

Ester

 

Acid

 

Hydrocarbon

 

Ether

Ester

The intermolecular bonds that link the complementary base pairs and help hold the in the two strands of the DNA double helix together are ________.

hydrogen bonds

Adenine is a purine.

 

True

 

False

true

A nucleotide consists of only a base and a sugar.

 

True

 

False

false

Which of the following is not an example of a macromolecule? (Hint: Macromolecule is the polymeric form.)

 

Polysaccharide

 

Protein

 

Nucleic acid

 

Amino acid

 

Enzyme

 

Amino acid

In the Five Kingdom classification system, human beings would be considered

animals

Which of these eukaryotic kingdoms consists primarily of unicellular organisms?

a. Animals

b. Fungi

c. Plants

d. Protista

e. Both fungi and protista.

Both fungi and protista.

Which of these kingdoms includes only prokaryotic organisms?

a. Animals

b. Fungi

c. Monera

d. Plants

e. Protista

8. If atoms with greatly differing electronegativities form a bond, that bond will be

polar

All eukaryotic organisms have

a nucleus

Which of the following functional groups are not commonly seen in biomolecules?

a. Alkyl halides

b. Amides

c. Carboxylic acids

d. Ethers

e. Phosphate esters

Alkyl halides

The water molecule is polar because:

a. Electrons are not distributed symmetrically in the molecule.

b. The hydrogen atoms are found on one "side" of the molecule.

c. Hydrogen is less electronegative than oxygen.

d. The hydrogen atoms are found on one "side" of the molecule and hydrogen is less electronegative than oxygen.

e. All of these are correct.

All of these are correct

Ionic compounds and polar covalent compounds tend to dissolve in water because of

ion dipole and dipole dipole interactions

Many of the properties of water can be accounted for by the fact that

a. it is polar

b. it forms hydrogen bonds

c. it is a bent molecule

d. all of these are true

all of these are true

How does the strength of hydrogen bonds compare with covalent bonds? a. Hydrogen bonds are much stronger than covalent bonds.

b. Hydrogen bonds are much weaker than covalent bonds.

c. Hydrogen bonds and covalent bonds have similar strengths.

d. The question cannot be answered without knowing which covalent bonds are being referred to

Hydrogen bonds are much weaker than covalent bonds.

Which will dissociate most in water, a weak acid or a strong acid?

A strong acid

Bases are

a. proton donors.

b. proton acceptors.

c. hydrogen bond donors.

d. hydrogen bond acceptors.

proton acceptors

Which has the greater Ka, a weak acid or a strong acid?

a. A weak acid.

b. A strong acid

c. They should dissociate about the same.

d. It's impossible to predict.

A strong acid

Which has the greater pKa, a weak acid or a strong acid?

a. A weak acid.

b. A strong acid

c. They should dissociate about the same.

d. It's impossible to predict

A weak acid

How many hydrogen bonds can water form?

4

Which of the following compounds are capable of hydrogen bonding with like molecules?

A) CH3CH2CH2CH2CH3

B) CH3CH2OCH2CH3

C) CH3NH2

D) HOCH2CH2OH

E) Both C and D are correct

Both C and D are correct

.Calculate the ratio of dihydrogen phosphate to hydrogen phosphate in blood at a pH 7.4. The Ka is 6.3 x10-8 .

1: 1.6

One liter of a solution pH 9 has how many more hydroxyl ions (OH-) than 1 L of a solution of pH 4?

100,000

Which of the following would not form a suitable buffer?

 

Carbonic acid/ bicarbonate

 

Phosphoric acid/ dihydrogen phosphate

 

Hydrochloric acid/ chloride

 

Bicarbonate/ carbonate

 

Acetic acid/ acetate

Hydrochloric acid/ chloride

A suitable buffer solution must consist of a blank acid and blank base

weak, conjugate

Which of the following species would form a buffer with HPO₄⁻²?

 

H₂PO₄⁻¹

 

Both A and B

 

H₃PO₄

 

All would form buffers with HPO₄⁻²

 

CO₃⁻²

H₂PO₄⁻¹

At pH 6.8 the H⁺ concentration is 4 times greater than at pH 7.4.  (T/F)

true

Which has the greater K_a, a weak acid or a strong acid?

strong

Polar covalent compounds tend to dissolve in water because of

dipole dipole interactions

What is the henderson hasselbach eq (what is ha what is a)

ph = pka log (a/ha) where ha is weak acid and a is conjugate vase

The following molecule is an example of which class of compounds?

CH₃CH₂CH₂COCH₃

ketone

The majority of Earth’s species belong to which of the following classifications?

Prokaryotes