Deck 3: Water: The Matrix of Life

Question 1

How many hydrogen bonds can water form?

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

Answer 1

D

Question 2

A hydrogen bond is best defined as:

A) A strong chemical bond between hydrogen and another element
B) A weak chemical bond between hydrogen and another element
C) A relatively strong electrostatic bond between hydrogen and oxygen or nitrogen
D) A weak electrostatic bond between hydrogen and oxygen or nitrogen
E) A bond between two hydrogens

Answer 2

C

Question 3

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

Answer 3

E

Question 4

Which of the following is not an example of noncovalent interactions between molecules?

A) Salt bridges
B) Hydrogen bonds
C) Hydrophobic interactions
D) Ionic bonds
E) Chemical bonds

Question 5

Which of the following factors is responsible for the fact that water is a liquid at room temperature?

A) Covalent O-H bonds
B) Ionic bonds
C) Hydrogen bonds
D) Hydrophobic bonding between water molecules
E) The molecular weight of water

Question 6

Which of the following properties of water promotes the relatively constant climate of earth?

A) High heat of fusion
B) High surface tension
C) High heat of vaporization
D) High heat capacity
E) A, C, and D are all important

Question 7

Which of the following compounds is amphipathic?

A) H₂O
B) CH₃CH₂CH₂CH₂CH₃
C) HOOCCOOH
D) CH₃CH₂CH₂CH₂COOH
E) Both A and D are correct

Question 8

Which of the following is the conjugate acid of the bicarbonate ion?

A)
B)
C)
D)
E)

Question 9

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

A) They are completely ionized in water
B) They are totally unionized in water
C) They are partially ionized in water
D) The dissociation constant is a function of pH
E) The dissociation constant is a function of solute concentration

Question 10

What is the pH of a solution where the concentration of hydrogen ions is 2 x 10^-5 molar?

A) 5
B) 2.5
C) 2
D) 4.7
E) 5.3

Question 11

Which of the following would not form a suitable buffer?

A) Acetic acid/ acetate
B) Carbonic acid/ bicarbonate
C) Bicarbonate/ carbonate
D) Hydrochloric acid/ chloride
E) Phosphoric acid/ dihydrogen phosphate

Question 12

Buffering capacity is directly proportional to which of the following factors?

A) Molecular weight of the buffer
B) Concentration of the conjugate acid of the buffer
C) Concentration of the conjugate base of the buffer
D) Concentration of both components of the buffer
E) The acid or base to be buffered against

Question 13

The sodium acetate/acetic acid buffer is 0.1 molar in sodium acetate and 0.5 molar in acetic acid. What is the concentration of the buffer?

A) 0.1 molar
B) 0.5 molar
C) 0.6 molar
D) 0.4 molar
E) Either A or B depending on whether acid or base is being added to the buffer.

Question 14

The pH of a solution that is 0.25 molar in acetic acid and 0.1 molar in sodium acetate is 4.36. What is the pKa of acetic acid?

A) 4.36
B) 4.76
C) 7.76
D) 3.76
E) 5.76

Question 15

The most important buffer in blood is __________.

A) Carbonate/bicarbonate buffer
B) Protein buffer
C) Phosphate buffer
D) Lactate buffer
E) Tartrate buffer

Question 16

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

A) Acidosis
B) Alkalosis
C) No change
D) First acidosis then rebounding alkalosis
E) First alkalosis then rebounding acidosos

Question 17

Salt bridges in proteins are an example of _________.

A) Hydrogen bonds
B) Ionic interactions
C) Hydrophobic interactions
D) van der Waals forces
E) London dispersion forces

Question 18

What is the osmolarity of a solution that is 0.25 molar in trisodium phosphate?

A) 0.25 osmolar
B) 0.5 osmolar
C) 0.75 osmolar
D) 1.0 osmolar
E) None of the above is correct

Question 19

Red blood cells are isotonic to a solution that is 0.9% sodium chloride. These same cells are _______________ to a solution that is 0.9% sodium sulfate.

A) Isotonic
B) Hypertonic
C) Hypotonic
D) Tonic
E) Nontonic

Question 20

Which of the following molecules would have a dipole moment?

A) CCl₄
B) CH₃CH₃
C) H₂
D) CHCl₃
E) I₂

Question 21

Which of the following molecules would form a micelle?

A) NaCl
B) CH₃COOH
C) CH₃CH₂CH₂CH₂CH₂CH₃
D) H₃PO₄
E) CH₃(CH₂)₁₀COO^- Na ⁺

Question 22

Which of the following molecules are weak acids?

A) HCl
B) CO₃^-2
C) HNO₃
D) HCO₃^-
E) Both B and D

Question 23

Which of the following ions would have the largest hydration sphere?

A) Li⁺
B) Na⁺
C) K⁺
D) Cs⁺
E) All would have the same size hydration sphere

Question 24

Hydration is best defined as

A) Covalent interaction between water and a solute
B) Noncovalent interaction between water and a solute
C) Salt formation in water
D) Ionization of a base to produce hydroxide ions
E) Both C and D are correct

Question 25

The noncovalent interaction between an amide and an alcohol would be which of the following?

A) Salt bridges
B) Hydrophobic
C) Hydrogen bonding
D) Both A and C are correct
E) All of the above are true

Question 26

Crenation would result when cells are placed in a ___________ solution.

A) Hypertonic
B) Hypotonic
C) Isotonic
D) Nontonic
E) Nonaqueous solvent

Question 27

Which of the following is not an important noncovalent interaction of living organisms?

A) Ionic interactions
B) Van der Waals interactions
C) Hydrogen bonds
D) Carbon hydrogen bonds
E) All are important

Question 28

Which of the following molecules would have unusually high heat capacities?

A) Ammonia
B) Methane
C) Methyl alcohol
D) Benzene
E) Both A and C are correct

Question 29

The hybridization of the water molecule is:

A) Sp³
B) Sp²
C) Sp
D) Unhybridized
E) Planar

Question 30

Which of the following is the strongest type of non-covalent force?

A)Dipole-Dipole
B)Dipole-Induced Dipole
C)Induced Dipole-Induced Dipole
D)London dispersion forces
E)Hydrogen bond

Question 31

Which of the following ions would have the strongest tendency to form an ion pair with carboxylate groups on the surface of a protein?

A) Lithium
B) Sodium
C) Potassium
D) All have the same tendency
E) These ions do not associate with proteins

Question 32

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

A) H₃PO₄
B) H₂PO₄^-1
C) CO₃^-2
D) All would form buffers with HPO₄^-2
E) Both A and B

Question 33

Water can form how many hydrogen bonds?

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

Question 34

Which of the following solutions will be isotonic with 3M sucrose?

A) 3M NaCl
B) 1 M Sodium sulfate
C) 1.5 M Proline
D) 2 M Sodium chloride
E) 1 M Magnesium sulfate

Question 35

Which of the following molecules is hydrophobic?

A) Sodium chloride
B) Ethyl alcohol
C) Hexane
D) Sucrose
E) Ammonia

Question 36

In biological systems buffers usually contain an excess of __________.

A) Weak base
B) Weak acid
C) The two components of the buffer are present in equal amounts
D) It would depend on the system
E) None of the above is correct

Question 37

The tendency of nonpolar molecules to aggregate in a water medium is called ________.

A) Crenation
B) Hydrophobic effect
C) Hydrophillic effect
D) Micellular effect
E) Amphiatic

Question 38

The high heat of fusion of water is due to its _______________.

A) Hydrogen bonding
B) High surface tension
C) High heat of vaporization
D) High heat capacity
E) A, C, and D are all important

Question 39

Which of the following is not a role of water in the body

A) Nutrient absorption
B) Nutrient transport
C) Waste product excretion
D) Temperature regulation
E) All are roles of water

Question 40

Which of the following species can form a buffer system?

A) Hydrochloric acid / Acetic acid
B) Acetic acid / Sodium chloride
C) Acetic acid / Ammonium chloride
D) Acetic acid/ Sodium acetate
E) Phosphoric acid / Sodium phosphate

Question 41

Which of the following are unusual properties of water that suit it to be the matrix
Of life?

A) Tetrahedral hybridization
B) Presence of oxygen
C) Thermal properties
D) Solvent characteristics
E) C and D

Question 42

What percentage of the world's water is drinkable

A) 100%
B) 60%
C) 3%
D) 1%
E) 97%

Question 43

The immediate effect of deforestation is

A) Drought
B) Erosion
C) Formation of grasslands
D) Formation of deserts
E) Increase in the water table

Question 44

Which of the following is not an effect of hydrogen bonding on the
Physical properties of water?

A) Increased boiling point
B) Increased heat of fusion
C) Increased melting point
D) Increased heat of vaporization
E) All are effects of hydrogen bonding

Question 45

What is a salt bridge?

Question 46

Describe an isotonic solution.

Question 47

Define the term hydrophobic effect.

Question 48

Define the term alkalosis.

Question 49

How many hydrogen bonds can methanol form with water?

Question 50

Bicarbonate is the principle buffer of the blood and phosphate is the principle buffer within cells. Explain.

Question 51

What is the effect of hyperventilation on blood pH?

Question 52

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

Question 53

Many molecules are polar but they do not form significant hydrogen bonds. What is unusual about water that hydrogen bonding becomes possible?

Question 54

If the total concentration of a buffer is known (and not the individual concentrations of the weak acid and its conjugate base) can the pH of the buffer be calculated?

Question 55

What is the maximum number of hydrogen bonds that water can form?

Question 56

Describe how you would increase the buffering capacity of a 0.1 M acetate buffer.

Question 57

What is a micelle? How do micelles form?

Question 58

What is the hydronium ion?

Question 59

Pure sugars are often crystalline solids. Frequently, the process used to concentrate aqueous solutions of sugars produces syrups rather than crystals. Explain.

Question 60

Water forms stronger hydrogen bonds than ammonia. Suggest a reason for this.

Question 61

Water has been described as the universal solvent. If this was strictly true could life have arisen in this medium? Explain

Question 62

Why can't seawater be used to water plants?

Question 63

The pH scale is valid only for water. Explain.

Question 64

Compounds such as the sugar trehalose are used as compatible solutes (i.e., water replacements) in desiccated organisms. What are the requirements for a substance that is to be used in this manner?

Question 65

When salt is spread on Jello (a mixture of gelatin and water), its consistency changes from a solid into a liquid. Explain.

Question 66

Explain why water has an unusually high heat capacity.

Question 67

Give an example of a molecule without an OH group that would be expected to have an unusually high heat capacity.

Question 68

Ammonia and water are both capable of forming hydrogen bonds. Why is water better at forming these bonds than ammonia?

Question 69

What is the major ionic structure for tyrosine at pH 7?
Tyrosine
NH₂ pKa = 9.11 COOH pKa 2.2 OH pKa = 10.07

Question 70

In water fatty acids form a micelle with the COO^- groups on the surface. The hydrophobic hydrocarbon tails are directed to the interior of the micelle. Explain.

Question 71

Explain why soaps that form micelles lower the surface tension of the water.

Question 72

If the osmotic pressure of a concentrated solution of sodium chloride is measured it is less than the calculated value. As the concentration of the sodium chloride is reduced the value of the osmotic pressure becomes closer and closer to the calculated value. Explain.

Question 73

Glucose is stored in cells as glycogen, an insoluble polymer. Hormone- triggered hydrolysis of glycogen produces glucose on demand. What advantages does this method of storage have for the cell?

Question 74

When plants are exposed to seawater they wilt and die. Explain.

Question 75

What is the osmolarity of a 1.3 M solution of sodium phosphate (Na₃PO₄)? Assume 85% ionization for this solution.

Question 76

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

Question 77

A solution that is 0.1M in acetic acid and 0.1 M in sodium acetate has a pH of 4.76. Determine the pK_a of acetic acid. What is the K_a for acetic acid?

Question 78

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

Question 79

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

Question 80

Sketch the titration curve of the amino acid tyrosine starting with the following structure:
The pKa values are as follows: amino group 9.11, carboxyl group = 2.2 and side chain hydroxyl group = 10.07.