Deck 22: Life and the Periodic Table

Question 1

Which element, by mass, is most abundant in the human body?

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

Answer 1

oxygen

Question 2

Nickel-cadmium batteries thrown into landfills can introduce cadmium ions into the ground water. Cadmium ions can replace ________ in bones, which can weaken them.

A) Na⁺
B) K⁺
C) Zn²⁺
D) Ca²⁺
E) Mg²⁺

Answer 2

Ca²⁺

Question 3

What is the dominant role played by calcium in the body?

A) maintains osmotic pressure
B) transmits nerve impulses
C) forms structural materials
D) a key component in enzymes
E) important in the function of the thyroid gland

Answer 3

forms structural materials

Question 4

One reason some metals have toxic effects is that they can replace other metals in a biomolecule and thereby inhibit or destroy the function of the biomolecule. Such replacement depends on the charge and size of the metal ion. For each of the following pairs of metal ions, identify the one that is larger.
(Ca²⁺, Mg²⁺)
(Ca²⁺, Zn²⁺)
(P³⁺, As³⁺)

A) Ca²⁺; Ca²⁺; P³⁺
B) Ca²⁺; Ca²⁺; As³⁺
C) Mg²⁺; Ca²⁺; As³⁺
D) Ca²⁺; Zn²⁺; P³⁺
E) Ca²⁺; Zn²⁺; As³⁺

Question 5

Tooth enamel is composed of the calcium compound called ________

A) hydrophilite.
B) apatite.
C) hydroxyapatite.
D) calcite.
E) andradite.

Question 6

Which statement describing the mechanisms by which sodium ions pass through cell membranes is not correct?

A) Groups of proteins form ion channels for sodium ions.
B) Sodium ions can be transported by Na⁺-K⁺ pumps.
C) Membrane proteins pump sodium ions through the membrane.
D) Sodium ions form complexes with nonpolar ligands that can diffuse through the membrane.
E) Sodium ions can diffuse directly through the membrane.

Question 7

Magnesium is found in which one of the following important biological molecules?

A) chlorophyll
B) hemoglobin
C) cytochrome C
D) ferredoxin
E) adenosine triphosphate

Question 8

Which element, by the number of atoms, is most abundant in the human body?

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

Question 9

The concentration of a trace essential element in the body is typically in the range of ________ per gram of body mass.

A) 1 $\mu$ g to 1 mg
B) 1 $\mu$ g to 10 mg
C) 10 $\mu$ g to 10 mg
D) 10 $\mu$ g to 100 mg
E) 100 $\mu$ g to 100 mg

Question 10

Which element, by the number of atoms, is least abundant in the human body?

A) sodium
B) calcium
C) potassium
D) magnesium
E) nitrogen

Question 11

An essential biological element ________

A) is any element detected in the organism.
B) stimulates essential biological functions.
C) is found in all organisms.
D) has beneficial physiological effects, and its absence impairs function of the organism.
E) is expensive.

Question 12

Which of the following is not a characteristic of a nonessential biological element?

A) detected in the body but has no clear biological function
B) has a stimulatory effect on biological functions
C) is incorporated into biological compounds because it is similar to essential elements
D) has clear biological functions
E) organisms require them for survival

Question 13

The concentration of a major essential element in the body is greater than ________ per gram of body mass.

A) 1 g
B) 10 mg
C) 1 mg
D) 10 $\mu$ g
E) 1 $\mu$ g

Question 14

Cell membranes are formed by ________

A) a lipid layer.
B) a lipid bilayer.
C) a phospholipid bilayer.
D) cellulose.
E) starch.

Question 15

The concentration of an ultratrace essential element in the body is less than ________ per gram of body mass.

A) 1 g
B) 10 mg
C) 1 mg
D) 10 $\mu$ g
E) 1 $\mu$ g

Question 16

Which ion is important in transmitting nerve impulses?

A) Na⁺
B) Mg²⁺
C) Fe²⁺
D) Zn²⁺
E) Li⁺

Question 17

Stomach acid has a pH of 0.80. What is the molar concentration of the acid, HCl?

A) 0.55 M
B) 0.25 M
C) 3.98 M
D) 1.82 M
E) 0.16 M

Question 18

The ion found in chlorophyll is ________

A) Zn²⁺.
B) Mg²⁺.
C) Ca²⁺.
D) Fe²⁺.
E) Cu²⁺.

Question 19

Which statement regarding mercury poisoning is not correct?

A) Mercury is readily transformed into methylmercury(II).
B) Methylmercury(II) is highly toxic because it can readily diffuse through the lipid bilayer of membranes.
C) Mercury(II) ions bind to sulfur-containing amino acids.
D) Mercury is stabilized and is not leached from amalgams used in dentistry.
E) Methylmercury(II) is a 2+ cation.

Question 20

Stomach acid is 0.16 M HCl. What is the pH of stomach acid?

A) 0.80
B) 8.0
C) -0.80
D) 0.69
E) -8.0

Question 21

Plants convert nitrogen into ammonia. This biological nitrogen fixation is effected by enzymes called nitrogenases. The enzymes assist in the transfer of electrons. The unbalanced reaction equation is
N₂(g) + H⁺(aq) + e^- $\rarr$ H₂(g) + NH₃(aq)
What is the stoichiometric coefficient for the electrons in the balanced reaction equation?

A) 1
B) 2
C) 4
D) 6
E) 8

Question 22

How much energy must be expended by a cell to transport 1 mole of sodium ions across a membrane with an electrochemical potential of 62 mV in order to maintain this potential?

A) 50 kJ
B) 260 kJ
C) 6.0 kJ
D) 250 kJ
E) 6,000 kJ

Question 23

Different concentrations of ions on either side of a cell membrane constitute a concentration cell, which is described by the Nernst equation given below. A cell must expend energy to maintain this concentration gradient by moving ions from one side of the membrane to the other. How much energy must be expended to transport 1 mole of sodium ions across a membrane when the sodium ion concentration is 0.10 M on one side of the membrane and 0.010 M on the other side, and the temperature is 37°C (body temperature)?
(Given: Na⁺ + e^- $\rarr$ Na, $E _ { \mathrm { red } } ^ { 0 }$ = -2.71 V; F = 96,485 C; 1 J = 1 C V; R = 8.315 J / (mol K))
$E = E { } ^ { \circ } - \frac { R T } { n F } \ln Q$

A) 50 kJ
B) 260 kJ
C) 6.0 kJ
D) 250 kJ
E) 6,000 kJ

Question 24

Calcium carbonate is used to form exoskeletons. It has a solubility-product constant of 5.0 * 10^-9. What is the molar concentration of calcium ions in a saturated solution of calcium carbonate?

A) 2.5 *10^-9 M
B) 7.1 *10^-5 M
C) 3.5 *10^-5 M
D) 5.0 *10^-9 M
E) 4.7 *10^-7 M

Question 25

Enzymes in plants convert nitrate into ammonia. The unbalanced half-reaction equation is given below. What is the change in oxidation number of nitrogen in this reaction?
NO₃^-(aq) + H₂O(l) + e^- $\rarr$ 0 NO₂^-(aq) + OH^-(aq)

A) 0
B) +5
C) +3
D) -2
E) -3

Question 26

What is the dominant role played by iodine in the body?

A) maintains osmotic pressure
B) transmits nerve impulses
C) forms structural materials
D) a key component in enzymes
E) important in the function of the thyroid gland

Question 27

Calcium carbonate is used to form exoskeletons. It has a solubility-product constant of 5.0 *10^-9. What is the mass of calcium ions dissolved in 1.0 L of a saturated solution of calcium carbonate?

A) 101 ng
B) 2.8 mg
C) 1.4 mg
D) 201 ng
E) 16 $\mu$ g

Question 28

Tooth enamel is composed of the mineral hydroxyapatite. It is essentially insoluble in water with K_sp = 2.3* 10^-59, but it reacts with weak acids in the mouth as described by one of the reaction equations below. You can determine the equilibrium constant, K, for this reaction from K_sp and K_w (the equilibrium constant for water autoionization). How do you do this?
Ca₅ (PO₄)₃(OH)(s) $\rightleftarrows$ Ca₅ (PO₄)₃⁺(aq) + OH^-(aq)
Ca₅ (PO₄)₃(OH)(s) + H⁺(aq) $\rightleftarrows$ Ca₅ (PO₄)₃⁺(aq) + H₂O(l)

A) K = K_wK_sp
B) K = K_w /K_sp
C) K = K_sp /K_w
D) K = K_w - K_sp
E) K = K_w + K_sp

Question 29

Plants convert nitrate into ammonia by using enzymes called ________

A) peptidases.
B) amylases.
C) anhydrases.
D) oxidases.
E) reductases.

Question 30

Tooth enamel is composed of the mineral hydroxyapatite. It is essentially insoluble in water with K_sp = 2.3 *10^-59, but it reacts with weak acids in the mouth as described by one of the reaction equations below. You can determine the equilibrium constant, K, for this reaction from K_sp and K_w (the equilibrium constant for water autoionization, K_w = 1.0 *10^-14). What is the value of K?
Ca₅ (PO₄)₃(OH)(s) $\rightleftarrows$ Ca₅ (PO₄)₃⁺(aq) + OH^-(aq)
Ca₅ (PO₄)₃(OH)(s) + H⁺(aq) $\rightleftarrows$ Ca₅ (PO₄)₃⁺(aq) + H₂O(l)

A) 2.3* 10^-73
B) 4.3 * 10⁴⁵
C) 2.3 * 10^-45
D) 1.1 *10^-14
E) 9.9 * 10^-15

Question 31

Plants convert nitrogen into ammonia. This biological nitrogen fixation is effected by enzymes called nitrogenases. The enzymes assist in the transfer of electrons. The unbalanced reaction equation is
N₂(g) + H⁺(aq) + e^- $\rarr$ H₂(g) + NH₃(aq)
What is the change in the oxidation number of nitrogen in this reaction?

A) +1
B) -3
C) +3
D) +2
E) -1

Question 32

The average concentration of calcium in the human body is 15 mg/g of body mass. What is the mass of calcium in the body of a person weighing 150 lb? (1 lb = 454 g)

A) 1.0 lb
B) 0.023 lb
C) 23 lb
D) 100 lb
E) 2.3 lb

Question 33

The average person has 15 mg of calcium per gram of body mass. How many pounds of calcium does a person weighing 175 lb contain? (1 lb = 454 g)

A) 22.5 lb
B) 0.225 lb
C) 2.63 lb
D) 10 lb
E) 15 lb

Question 34

The concentration of sodium in the human body is approximately 1.5 mg/g of body mass. What is this concentration in ppm (parts per million)?

A) 1.5 * 10⁶ ppm
B) 1.5 * 10^-3 ppm
C) 0.015 ppm
D) 1,500 ppm
E) 150 ppm

Question 35

Urea is a waste product produced when the body metabolizes protein. What is the oxidation number of nitrogen in urea, (NH₂)₂CO?

A) +3
B) -3
C) 1
D) -1
E) -4

Question 36

Different concentrations of ions on either side of a cell membrane constitute a concentration cell, which is described by the Nernst equation given below. What is the electrochemical potential across a membrane when the sodium ion concentration is 0.10 M on one side of the membrane and 0.010 M on the other side, and the temperature is 37°C (body temperature)?
(Given: Na⁺ + e^- $\rarr$ Na, $E _ { \mathrm { red } } ^ { 0 }$ = -2.71 V; F = 96,485 C; 1 J = 1 C V; R = 8.315 J / (mol K))
$E = E { } ^ { \circ } - \frac { R T } { n F } \ln Q$

A) 61.5 mV
B) 26.7 mV
C) 2.65 V
D) 2.68 V
E) 2.98 V

Question 37

Enzymes in plants convert nitrate into ammonia. The unbalanced half-reaction equation is given below. What is the stoichiometric coefficient of the electrons, e^-, in the balanced reaction equation?
NO₃^-(aq) + H₂O(l) + e^- $\rarr$ NO₂^-(aq) + OH^-(aq)

A) 1
B) 2
C) 3
D) 4
E) 5

Question 38

Plants react urea with water to produce ammonia and carbon dioxide. This reaction is an example of a ________ reaction.

A) redox
B) metathesis
C) hydrolysis
D) combustion
E) precipitation

Question 39

Enzymes in plants convert nitrate into ammonia. The unbalanced half-reaction equation is given below. What is the stoichiometric coefficient of the hydroxide in the balanced reaction equation?
NO₃^-(aq) + H₂O(l) + e^- $\rarr$ NO₂^-(aq) + OH^-(aq)

A) 1
B) 2
C) 3
D) 4
E) 5

Question 40

Plants convert nitrogen into ammonia. This biological nitrogen fixation is effected by enzymes called nitrogenases. The enzymes assist in the transfer of electrons. The unbalanced reaction equation is
N₂(g) + H⁺(aq) + e^- $\rarr$ H₂(g) + NH₃(aq)
What is the stoichiometric coefficient for ammonia in the balanced reaction equation?

A) 1
B) 2
C) 4
D) 6
E) 8

Question 41

Selenocysteine is an amino acid that gets incorporated into proteins that serve as antioxidants. Evidence points to a need for a minimum daily dose of selenium of 55 $\mu$ 10g. How many moles of selenocysteine (C₃H₇NO₂Se, 168 g/mol) can be synthesized using this amount of selenium?

A) 3.3 * 10^-7 mol
B) 7.0 *10^-7 mol
C) 3.3 * 10^-4 mol
D) 7.0 * 10^-4 mol
E) 3.7 *10^-7 mol

Question 42

Selenium can substitute for sulfur in the amino acid cysteine to make the amino acid selenocysteine because ________

A) sulfur and selenium both begin with s.
B) their atomic symbols are similar.
C) both have about the same atomic radius.
D) both have the same valence electron configuration.
E) both have about the same ionization potential.

Question 43

The concentration of Li in the human body is approximately 30 ng/g body mass. How many milligrams of Li are there in a person weighing 170 lb? 1 lb = 454 g

A) 2.3 mg
B) 5,100 mg
C) 23 mg
D) 1.1 mg
E) 0.0023 mg

Question 44

Fluoridation to prevent tooth decay replaces ________ with fluoride in hydroxyapatite.

A) hydroxide
B) phosphate
C) phosphide
D) calcium
E) water

Question 45

Selenium is an ultratrace element that is essential for life. It is used in the synthesis of ________, which is ________.

A) selenocysteine; a lipid
B) cysteine; an amino acid
C) selenocysteine; an amino acid
D) selenocysteine; a fatty acid
E) selenothymine; a nucleic acid base

Question 46

Copper is a trace metal in the human body with a typical concentration of 110 mg in 75 kg of body mass. What is this concentration in units of parts per million (ppm)?

A) 1.5 * 10^-6 ppm
B) 1.5 ppm
C) 1.1 * 10^-5 ppm
D) 1.1 * 10^-7 ppm
E) 150 ppm

Question 47

The active site of an enzyme typically contains ________

A) an alkali metal.
B) an alkaline earth metal.
C) a transition metal.
D) an actinide metal.
E) a lanthanide metal.

Question 48

Chromium is an ultratrace metal in the human body with a typical concentration of 5.0 mg in
75 kg of body mass. What is this concentration in units of parts per billion (ppb)?

A) 6.7 * 10⁷ ppb
B) 6.7 * 10⁴ ppb
C) 67 ppb
D) 0.067 ppb
E) 0.67 ppb

Question 49

The release of radioactive cesium-137 into the environment by the nuclear accident at Chernobyl produced a health hazard because cesium ions can substitute for ________ in plants, making them unsafe for human consumption.

A) Mg²⁺
B) K⁺
C) Ca²⁺
D) Li⁺
E) H⁺

Question 50

A radioactive isotope that emits the shortest range particles and therefore would be a good choice for implantation therapy most likely decays via ________

A) alpha particles.
B) beta particles.
C) positrons.
D) gamma rays.
E) X-rays.

Question 51

Barium is a nonessential element in the human body, but some organisms build exoskeletons using barium sulfate, which has a K_sp of 1.1 * 10^-10 at 25°C. What is the mass of barium in 1.0 L of a saturated solution of barium sulfate at 25°C?

A) 4.1 $\mu$ g
B) 1.4 mg
C) 3.7 mg
D) 7.3 $\mu$ g
E) 15 ng

Question 52

An enzyme catalyzes the decomposition of hydrogen peroxide at 20°C. The activation energy for the uncatalyzed reaction is 75.3 kJ/mol. The activation energy for the catalyzed reaction is 29.3 kJ/mol. By what factor is the rate of the reaction increased by the enzyme? Use the Arrhenius equation, which is given below, to determine the ratio of rate constants, k_catalyzed/k_uncatalyzed.
(R = 8.315 J / (mol K))
$k = A \exp \left( - \frac { E _ { a } } { R T } \right)$

A) 1.6 * 10⁵
B) 1.6 * 10¹¹
C) 1.6 * 10⁸
D) 7.6
E) 6,100

Question 53

Urease is an enzyme that catalyzes the decomposition of urea to ammonia and carbon dioxide. The rate constant for the uncatalyzed reaction is 4.0*10^-11/s at 22°C. Urease increases the rate constant to a value of 8.0 *10^-5/s. Use the Arrhenius equation, which is given below, to determine the difference in the activation energies E_uncatalyzed - E_catalyzed. (R = 8.315 J / (mol K)) $k = A \exp \left( - \frac { E _ { a } } { R T } \right)$

A) 23 kJ/mol
B) 2.3 kJ/mol
C) 15 kJ/mol
D) 36 kJ/mol
E) 51 kJ/mol

Question 54

Selenium, an ultratrace element, is used in the synthesis of selenocysteine, which is ________

A) an amino acid.
B) a lipid.
C) a fatty acid.
D) a carbohydrate.
E) a nucleic acid base.

Question 55

Adding fluoride ions to toothpaste and drinking water converts the mineral in tooth enamel, hydroxyapatite, to fluoroapatite. This conversion is beneficial in preventing tooth decay because fluoroapatite ________

A) solubility is less pH dependent.
B) makes strong hydrogen bonds.
C) prevents halitosis.
D) repels decay-producing bacteria.
E) kills decay-producing bacteria.

Question 56

Hydroxyapatite, which is a component of tooth enamel, is very insoluble in water. For the following reaction, K_sp = 2.3 *10^-59.
Ca₅(PO₄)₃(OH)(s) $\rightleftarrows$ Ca₅(PO₄)₃⁺(aq) + OH^-(aq)
What is the molar concentration of Ca₅(PO₄)₃⁺ when the pH of the mouth is 4.0?

A) 2.3 * 10^-49 M
B) 2.3 * 10^-59 M
C) 2.3* 10^-55 M
D) 2.3 *10^-63 M
E) 0, teeth don't dissolve!

Question 57

Radioactive ⁹⁰Sr can substitute for ________ in the human body.

A) Na⁺
B) Ca²⁺
C) K⁺
D) S^2-
E) Se²⁺

Question 58

Iodine's role is very specific. It is incorporated into a hormone, ________, that regulates energy production and use.

A) melatonin
B) thyroxine
C) dopamine
D) insulin
E) iodocin

Question 59

Chromium is an ultratrace metal in the human body. The typical concentration is 5.0 mg in 70.0 kg of body mass. This concentration can be expressed as ________

A) 0.071 ppm or 71 ppb.
B) 71 ppm or 0.071 ppb.
C) 14 ppm or 14,000 ppb.
D) 0.71 ppm or 710 ppb.
E) 5.0 ppm or 500 ppb.

Question 60

Adding fluoride ions to toothpaste and drinking water to prevent tooth decay is effective because fluoride ________

A) kills decay-producing bacteria.
B) produces stronger teeth.
C) reduces the solubility of tooth enamel at low pH.
D) reduces the solubility of tooth enamel at high pH.
E) prevents halitosis.

Question 61

Nitrogen is a major essential element in the human body. Which biomolecules incorporate nitrogen?

Question 62

Hearing aid batteries utilize a zinc/air electrochemical cell. The reduction half-reactions and standard reduction potentials for this cell are given below. What is the standard cell potential of a zinc/air cell?
Zn(OH)₂(s) + 2e^- $\rarr$ Zn(s) + 2OH^-(aq)
-1.249 V
O₂(g) + 2H₂O(l) + 4e^- $\rarr$ 4OH^-(aq)
+0.401 V

A) -0.848 V
B) +1.500 V
C) +0.848 V
D) +1.650 V
E) -1.650 V

Question 63

The isotope ²⁰¹Th is used in the diagnosis of heart disease. It has a first-order rate constant, k, of 9.49 *10^-3 h^-1. What is the half-life for ²⁰¹Th?

A) 73 hr
B) 0.014 hr
C) 9.49 * 10^-3 hr
D) 7.3 hr
E) 1.4 hr

Question 64

Pacemakers implanted in the chests of patients with certain heart conditions are powered by a lithium/iodine PVP battery, where PVP represents polyvinylpyridine. The cell reaction and standard cell potential are given below. The standard reduction potential for Li/Li+ is -3.05 V. What species is oxidized in this reaction?
2Li(s) + I₂:PVP(s) $\rarr$ 2LiI(s) + PVP(s)
3.59 V

A) Li
B) I₂
C) I₂:PVP
D) PVP
E) LiI

Question 65

Technetium can be produced in a nuclear reactor for medical applications and is given the symbol ^99mTc. What does the m stand for?

A) microstate
B) metastable excited state
C) microstable excited state
D) medical isotope
E) massive isotope

Question 66

Radioactive tritium, ³H, is used as a tracer in many biological experiments. It decays by $\beta$ emission. What is the product of this decay?

A) (³He)
B) (⁴He)..
C) (²H)
D) (¹⁴C)
E) (²H)..

Question 67

Hearing aid batteries utilize a zinc/air electrochemical cell. The reduction half-reactions and standard reduction potentials for this cell are given below. Write the balanced reaction equation for the cell and report the sum of the stoichiometric coefficients.
Zn(OH)₂(s) + 2e^- $\rarr$ Zn(s) + 2OH^-(aq)
-1)249 V
O₂(g) + 2H₂O(l) + 4e^- $\rarr$ 4OH^-(aq)
+0.401 V

A) 4
B) 5
C) 6
D) 7
E) 8

Question 68

Hearing aid batteries utilize a zinc/air electrochemical cell. The reduction half-reactions and standard reduction potentials for this cell are given below. What is the oxidizing agent in the cell reaction?
Zn(OH)₂(s) + 2e^- $\rarr$ Zn(s) + 2OH^-(aq)
-1.249 V
O₂(g) + 2H₂O(l) + 4e^- $\rarr$ utilize4OH^-(aq)
+0.401 V

A) oxygen
B) zinc
C) zinc hydroxide
D) hydroxide
E) water

Question 69

Pacemakers implanted in the chests of patients with certain heart conditions are powered by a lithium/iodine PVP battery, where PVP represents polyvinylpyridine. The cell reaction and standard cell potential are given below. The standard reduction potential for Li/Li+ is -3.05 V. What is the standard reduction potential for the iodine PVP half-reaction?
2Li(s) + I₂:PVP(s) $\rarr$ 2LiI(s) + PVP(s)
3.59 V

A) +1.50 V
B) -6.64 V
C) -0.54 V
D) +6.64 V
E) +0.54 V

Question 70

Rhenium-186 has medical applications. It decays by $\beta$ emission. What isotope is formed from this decay?

A)
( ${ } _ { 75 } ^ { 187 } \mathrm { Re }$ )
B)
( ${ } _ { 76 } ^ { 186 } \mathrm { Os }$ )
C)
( ${ } _ { 76 } ^ { 187 } \mathrm { Os }$ )
D)
( ${ } _ { 75 } ^ { 185 } \mathrm { Re }$ )
E)
( ${ } _ { 75 } ^ { 185 } \mathrm { Os }$ )

Question 71

A patient is injected with a 5.0 $\mu$ M solution of gallium citrate containing radioactive gallium-68 for a PET study. The half-life of gallium-68 is 9.4 hr. How long does it take for the activity of this isotope to drop to 1% of its initial value?

A) 18 hr
B) 25 hr
C) 32 hr
D) 41 hr
E) 62 hr

Question 72

Thallium-201 is used in cardiac imaging. It decays by electron capture. What isotope is produced when thallium-201 captures an electron?

A) thallium-202
B) lead-201
C) lead-202
D) mercury-201
E) mercury-202

Question 73

Hearing aid batteries utilize a zinc/air electrochemical cell. The reduction half-reactions and standard reduction potentials for this cell are given below. What species are oxidized and reduced in the cell reaction?
Zn(OH)₂(s) + 2e^- $\rarr$ Zn(s) + 2OH^-(aq)
-1)249 V
O₂(g) + 2H₂O(l) + 4e^- $\rarr$ 4OH^-(aq)
+0.401 V

A) Oxygen is reduced and zinc is oxidized.
B) Zinc is reduced and oxygen is oxidized.
C) Zinc hydroxide is reduced and oxygen is oxidized.
D) Zinc hydroxide is reduced and hydroxide is oxidized.
E) Water is reduced and zinc is oxidized.

Question 74

Hearing aid batteries utilize a zinc/air electrochemical cell. The reduction half-reactions and standard reduction potentials for this cell are given below. What is the reducing agent in the cell reaction?
Zn(OH)₂(s) + 2e^- $\rarr$ Zn(s) + 2OH^-(aq)
-1.249 V
O₂(g) + 2H₂O(l) + 4e^- $\rarr$ 4OH^-(aq)
+0.401 V

A) oxygen
B) zinc
C) zinc hydroxide
D) hydroxide
E) water

Question 75

The cation BiO⁺ is found in some over-the-counter antacids. Draw the Lewis structure of this cation that satisfies the octet rule for both atoms. Based on this Lewis structure, this cation has ________ of nonbonding electrons.

A) a triple bond and two pairs
B) a single bond and six pairs
C) a double bond and three pairs
D) a single bond and four pairs
E) a quadruple bond and one pair

Question 76

Ions need to move in and out of cells through cell membranes. Direct diffusion of ions through the lipid bilayer of the cell membrane is difficult because ions are not soluble in these nonpolar regions. Describe three mechanisms by which ions are transported through cell membranes.

Question 77

Iron accumulation in the human body has been implicated in some diseases. A chelating ligand sometimes is administered to treat these diseases. This treatment works because the ligand ________

A) oxidizes iron(II) to iron(III).
B) reduces iron(III) to iron(II).
C) precipitates the iron.
D) binds the iron to a protein.
E) forms a complex with the iron.

Question 78

Shape memory alloys are used in ________

A) artificial joints.
B) stents to prop open arteries.
C) sutures to close wounds.
D) braces for teeth.
E) screws to connect broken bones.

Question 79

Calcium is a major essential element in the human body. What is the dominant role played by calcium?

Question 80

The essential elements found in the human body are classified as major, trace, and ultratrace based on their concentration levels. What are the concentration ranges that define each of these classifications?