Question 1

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

Accepted Answer

Iodine is necessary for the synthesis of thyroid hormones, which play a critical role in regulating metabolism and growth and development in the body.

Question 2

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

Accepted Answer

The answer of Nitrogen is a major essential element in...

Question 3

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_un_catalyzed - E_catalyzed. (R = 8.315 J/mol K)

Accepted Answer

The answer of Urease is an enzyme that catalyzes the...

Question 4

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?

Accepted Answer

The answer of Calcium carbonate is used to form exoskeletons....

Question 5

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

Accepted Answer

The answer of What is the dominant role played by...

Question 6

Which statement regarding mercury poisoning is not correct?

Accepted Answer

The answer of Which statement regarding mercury poisoning is not...

Question 7

The active site of an enzyme typically contains __________

Accepted Answer

The active sites of enzymes often contain transition metal ions, such as copper, iron, or zinc, that play an important role in the enzyme's catalytic activity.

Question 8

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. How many grams of barium are there in 1.0 L of a saturated solution of barium sulfate at 25°C?

Accepted Answer

The answer of Barium is a nonessential element in the...

Question 9

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( )

Accepted Answer

The equilibrium constant for the reaction can be expressed as: K = [Ca2+][HPO42-][OH-]/[CaHPO4] At equilibrium, the concentration of CaHPO4(s) can be assumed to be constant. Thus, the equilibrium constant can be simplified as: K = [Ca2+][HPO42-][OH-] The concentration of H2O does not appear in the expression for K as it is a pure liquid and its activity is considered to be equal to 1. The equilibrium constant for water autoionization can be expressed as: Kw = [H+][OH-] Rearranging the expression gives: [OH-] = Kw/[H+] Substituting this into the expression for K gives: K = [Ca2+][HPO42-](Kw/[H+]) K = Kw[Ca2+][HPO42-]/[H+] Thus, K = Kw/Ksp K = K_sp/K_w, where Kw is the equilibrium constant for water autoionization, Ksp is the solubility product constant for CaHPO4, K_sp is the solubility product constant for CaHPO4 and K_w is the equilibrium constant for water autoionization. Therefore, the correct choice is C (K = K_sp/K_w).

Question 10

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 its value? 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( )

Accepted Answer

The equilibrium constant can be found using the equation:
K = [Ca2+][HPO42-]/[CaHPO4]

Using the given reaction equations, we can determine the concentrations of the products and reactants at equilibrium. At equilibrium, the concentration of Ca2+ and OH- is equal to the solubility of hydroxyapatite in water, which is essentially equal to zero. Therefore, we can assume that the concentration of Ca2+ and OH- at equilibrium is negligible compared to the concentration of HPO42- and H+.

So, we can simplify the equation to:
K = [HPO42-]/[CaHPO4]

We can also use the equilibrium constant for water autoionization, Kw, to find the concentration of H+ at equilibrium. At room temperature, Kw = 1.0 x 10^-14. Therefore, [H+][OH-] = 1.0 x 10^-14. Since the concentration of OH- at equilibrium is negligible, we can assume that [H+] = 1.0 x 10^-14.

Therefore, we can use the equation for the dissociation of H3PO4 to find the concentration of HPO42-:
H3PO4 + H2O ↔ HPO42- + H3O+
Ka = [HPO42-][H3O+]/[H3PO4]
Ka = 7.5 x 10^-3

At equilibrium, [HPO42-]/[H3PO4] = Ka/[H+]
[HPO42-]/[H3PO4] = 7.5 x 10^-3/1.0 x 10^-14 = 7.5 x 10^11

Substituting this value into the equation for K, we get:
K = [HPO42-]/[CaHPO4]
K = (7.5 x 10^11)/1 = 7.5 x 10^11

Therefore, the answer is C.

Question 11

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.

Accepted Answer

The answer of The cation BiO⁺ is found in some...

Question 12

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?

Accepted Answer

The answer of The essential elements found in the human...

Question 13

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?

Accepted Answer

The answer of A patient is injected with a 5.0...

Question 14

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)

Accepted Answer

The answer of An enzyme catalyzes the decomposition of hydrogen...

Question 15

Which ion is important in transmitting nerve impulses?

Accepted Answer

Na+ ions are important in transmitting nerve impulses. When a nerve impulse reaches the end of a nerve cell, Na+ channels open, allowing Na+ ions to enter the cell, creating an action potential that travels down the nerve cell and allows for the transmission of the nerve impulse. None of the other ions listed have a significant role in nerve impulse transmission.

Question 16

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

Accepted Answer

Alpha particles have the shortest range and deposit their energy within a very small area, making them a good choice for implantation therapy. They have a high linear energy transfer (LET) and are highly ionizing, which can lead to localized damage to cancer cells. Beta particles, positrons, gamma rays, and X-rays have longer ranges and are less suitable for implantation therapy.

Question 17

The ion found in chlorophyll is __________

Accepted Answer

The ion found in chlorophyll is magnesium (Mg), which is represented by the chemical formula Mg²⁺.

Question 18

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.

Accepted Answer

The answer of Ions need to move in and out...

Question 19

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

Accepted Answer

The answer of Calcium is a major essential element in...

Question 20

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 __________

Accepted Answer

To convert mg/kg to ppm or ppb, we need to know what mass of the body is being considered. Assuming the mass of the body to be 70.0 kg, we can calculate the concentration as follows:

Concentration in ppm = (5.0 mg/70.0 kg) x 1,000,000
= 71.4 ppm (rounded to one decimal place)

Concentration in ppb = (5.0 mg/70.0 kg) x 1,000,000,000
= 71,429 ppb (rounded to the nearest whole number)

Therefore, the best choice is A, which correctly expresses the concentration as 0.071 ppm or 71 ppb.

Quiz 22: Life and the Periodic Table

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

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

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?

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

Which statement regarding mercury poisoning is not correct?

The active site of an enzyme typically contains __________

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. How many grams of barium are there in 1.0 L of a saturated solution of barium sulfate at 25°C?

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.

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?

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?

Which ion is important in transmitting nerve impulses?

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

The ion found in chlorophyll is __________

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.

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

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 __________

Quiz 22: Life and the Periodic Table

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

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

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?

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

Which statement regarding mercury poisoning is not correct?

The active site of an enzyme typically contains __________

Barium is a nonessential element in the human body, but some organisms build exoskeletons using barium sulfate, which has a Ksp of 1.1 *10-10 at 25°C. How many grams of barium are there in 1.0 L of a saturated solution of barium sulfate at 25°C?

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.

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?

A patient is injected with a 5.0 μ\muμ 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?

Which ion is important in transmitting nerve impulses?

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

The ion found in chlorophyll is __________

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.

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

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 __________

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?

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. How many grams of barium are there in 1.0 L of a saturated solution of barium sulfate at 25°C?

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 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?