Question 1

Which of the following best explains why water is considered a unique molecule in biological systems?

Accepted Answer

Water's polarity and ability to form hydrogen bonds give it unique properties essential for life.

Question 2

An atom of carbon has 6 protons, 6 neutrons, and 6 electrons. What is its atomic number and approximate atomic mass?

Accepted Answer

Atomic number: 6, Atomic mass: 12

Question 3

Which of the following elements makes up the largest percentage of body mass in humans?

Accepted Answer

Oxygen

Question 4

A radioactive isotope of carbon, carbon-14, has a half-life of 5,730 years. If you start with 100 grams of carbon-14, how much will remain after 11,460 years?

Accepted Answer

$$25\ 	ext{grams}$$

Question 5

Which statement best describes a compound?

Accepted Answer

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

Question 6

Which of the following is a trace element required in minute amounts for human life?

Accepted Answer

Iron

Question 7

What is the charge of an ion that has 11 protons and 10 electrons?

Accepted Answer

$$+1$$

Question 8

Which type of chemical bond involves the sharing of electron pairs between atoms?

Accepted Answer

Covalent bond

Question 9

Why are weak chemical interactions, such as hydrogen bonds and van der Waals forces, important in biological molecules?

Accepted Answer

They allow biological molecules to maintain their functional forms and enable reversible interactions.

Question 10

Which of the following best describes electronegativity?

Accepted Answer

The ability of an atom to attract electrons in a covalent bond.

Question 11

A sodium atom ($$	ext{Na}) $$loses one electron to become a sodium ion ($$	ext{Na}^+). $$What type of ion is formed and what is its charge?

Accepted Answer

Cation, $$+1$$

Question 12

Which of the following best explains why arsenic is toxic to humans?

Accepted Answer

Arsenic disrupts biological processes even at low concentrations.

Question 13

Which of the following equations correctly represents the photosynthesis reaction?

Accepted Answer

$$6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6$ + 6O_2$$

Question 14

If an atom has a full valence shell, what is its chemical reactivity?

Accepted Answer

It is chemically inert and unlikely to form bonds.

Question 15

Which of the following best describes a reversible chemical reaction?

Accepted Answer

A reaction where products can revert to reactants and equilibrium is reached when forward and reverse rates are equal.

Question 16

Which of the following is true about isotopes of an element?

Accepted Answer

Isotopes have the same number of protons but different numbers of neutrons.

Question 17

Which of the following best explains why sodium chloride ($$	ext{NaCl}) $$dissociates in water?

Accepted Answer

Water's polarity allows it to surround and separate the sodium and chloride ions.

Question 18

Which of the following best describes the role of kidneys in maintaining pH balance in the body?

Accepted Answer

Kidneys regulate the concentration of bicarbonate ions ($$HCO_3$$^-$$) to buffer blood pH.

Question 19

Which of the following is a real-world application of radioactive isotopes in medicine?

Accepted Answer

Radioactive isotopes are used as tracers to diagnose and treat diseases.

The Chemical Context of Life: Elements, Atoms, and Molecules

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