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

Question 1

Which of the following best describes a compound?

Accepted Answer

A substance consisting of two or more elements in a fixed ratio, held together by chemical bonds.

Question 2

Which four elements make up approximately 96% of the human body’s mass?

Accepted Answer

Oxygen, Carbon, Hydrogen, Nitrogen

Question 3

An atom of sodium (Na) has 11 protons and 12 neutrons. What is its atomic number and mass number?

Accepted Answer

Atomic number: 11, Mass number: 23

Question 4

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 5

Which type of chemical bond is formed when two atoms share a pair of valence electrons equally?

Accepted Answer

Nonpolar covalent bond

Question 6

What is the main reason water (H$$_2O) $$molecules are polar?

Accepted Answer

Oxygen is more electronegative than hydrogen, causing unequal sharing of electrons.

Question 7

Which of the following best explains why sodium chloride (NaCl) forms an ionic bond?

Accepted Answer

Sodium donates an electron to chlorine, resulting in oppositely charged ions that attract each other.

Question 8

Which of the following is a trace element essential for human health, even though it makes up less than 0.01% of body mass?

Accepted Answer

Iron (Fe)

Question 9

A radioactive isotope is useful in medical imaging because:

Accepted Answer

It decays spontaneously, emitting detectable particles or energy.

Question 10

Which of the following best describes a hydrogen bond?

Accepted Answer

A weak attraction between a hydrogen atom covalently bonded to one electronegative atom and another electronegative atom.

Question 11

Which of the following chemical equations represents cellular respiration?

Accepted Answer

$$\mathrm{C_6H_{12}O_6$} + 6\ \mathrm{O_2$} ightarrow 6\ \mathrm{CO_2$} + 6\ \mathrm{H_2O} + 	ext{Energy}$$

Question 12

If an atom has 7 electrons, how many valence electrons does it have, and to which group in the periodic table does it belong?

Accepted Answer

5 valence electrons; Group 15 (V)

Question 13

Which property of water is primarily responsible for its ability to dissolve many substances?

Accepted Answer

Its polarity, which allows it to form hydrogen bonds with ions and polar molecules.

Question 14

A patient is injected with a radioactive isotope for a PET scan. Which property of the isotope is most important for this application?

Accepted Answer

It emits detectable radiation as it decays.

Question 15

Which of the following best explains why the shape of a molecule is important in biology?

Accepted Answer

Molecular shape determines how molecules recognize and respond to each other.

Question 16

During photosynthesis, which of the following chemical equations correctly represents the process?

Accepted Answer

$$6\ \mathrm{CO_2$} + 12\ \mathrm{H_2O} + 	ext{Energy} ightarrow \mathrm{C_6H_{12}O_6$} + 6\ \mathrm{O_2$} + 6\ \mathrm{H_2O}$$

Question 17

Which of the following statements about chemical equilibrium is correct?

Accepted Answer

At equilibrium, the rates of the forward and reverse reactions are equal.

Question 18

A molecule of ammonia (NH$$_3) $$can form hydrogen bonds with water molecules. Which atom in ammonia is involved in hydrogen bonding with water?

Accepted Answer

Nitrogen, because it is highly electronegative and can attract hydrogen from water.

Question 19

Which of the following best describes the difference between a cation and an anion?

Accepted Answer

A cation is positively charged, while an anion is negatively charged.

Question 20

Which of the following scenarios best illustrates the concept of a reversible chemical reaction?

Accepted Answer

Carbonic acid in blood can dissociate into carbon dioxide and water, and these can recombine to form carbonic acid.

The Chemical Context of Life: Foundations for General Biology

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