Question 1

Which of the following statements best explains why water is considered the 'universal solvent' in biological systems?

Accepted Answer

Water's polarity allows it to dissolve many ionic and polar substances by surrounding them with hydration shells.

Question 2

A patient is diagnosed with goiter, a swelling of the thyroid gland. Which trace element deficiency is most likely responsible for this condition?

Accepted Answer

Iodine

Question 3

Which of the following best describes a compound?

Accepted Answer

A substance consisting of two or more different elements in a fixed ratio.

Question 4

Which property of water is primarily responsible for the phenomenon of surface tension?

Accepted Answer

Hydrogen bonding between water molecules

Question 5

A radioactive isotope is used in a PET scan to diagnose a heart disorder. What property of radioactive isotopes makes them useful for this purpose?

Accepted Answer

They emit energy that can be detected by imaging instruments.

Question 6

Which of the following equations correctly represents the relationship between the atomic number ($$Z$$), the number of protons ($$p$$), and the number of neutrons ($$n) in an $$atom with mass number ($$A$$)?

Accepted Answer

$$A = Z + n$$

Question 7

Why does ice float on liquid water?

Accepted Answer

Ice is less dense than liquid water because hydrogen bonds hold water molecules farther apart in the solid state.

Question 8

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of electron pairs between atoms.

Question 9

A solution has a pH of 4. How does its hydrogen ion concentration compare to a solution with a pH of 7?

Accepted Answer

It is 1,000 times higher.

Question 10

Which of the following is a real-world example of a buffer system in the human body?

Accepted Answer

The carbonic acid-bicarbonate system in blood

Question 11

Which of the following best explains why trace elements are added to food and water?

Accepted Answer

To help preserve food, make it more nutritious, and improve its appearance.

Question 12

Which of the following statements about chemical reactions is correct?

Accepted Answer

Chemical reactions only rearrange matter; they do not create or destroy it.

Question 13

Which of the following best describes the role of electrons in chemical bonding?

Accepted Answer

Electrons in the outermost shell (valence electrons) determine an atom's chemical properties and bonding behavior.

Question 14

A scientist is studying the effects of ocean acidification on coral reefs. Which chemical process is directly responsible for lowering the pH of ocean water?

Accepted Answer

Dissolution of atmospheric $$CO_2$$ into seawater, forming carbonic acid

Question 15

Which of the following is an example of a polar covalent bond?

Accepted Answer

The bond between oxygen and hydrogen in a water molecule

Question 16

Which of the following best explains why living cells cannot distinguish between isotopes of the same element?

Accepted Answer

Isotopes have the same number of electrons and thus the same chemical behavior.

Question 17

Which of the following is a consequence of water's high specific heat for life on Earth?

Accepted Answer

Water's temperature remains relatively stable, helping to moderate Earth's climate and maintain stable environments for organisms.

Question 18

Which of the following best describes the difference between an ionic bond and a covalent bond?

Accepted Answer

An ionic bond involves the transfer of electrons from one atom to another, resulting in oppositely charged ions that attract each other, while a covalent bond involves the sharing of electron pairs between atoms.

Question 19

A molecule of water ($$H_2O) is $$held together by which type of bond, and what type of bond forms between different water molecules?

Accepted Answer

Covalent bonds within the molecule; hydrogen bonds between molecules

Question 20

Which of the following best explains why water is essential for life as we know it?

Accepted Answer

Water's unique properties, such as cohesion, high specific heat, and its role as a solvent, support the chemical reactions necessary for life.

Chapter 2: The Chemical Basis of Life – Elements, Atoms, and Compounds

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