Question 1

Which of the following statements best describes an element?

Accepted Answer

An element is a substance that cannot be broken down into other substances by chemical reactions.

Question 2

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

Accepted Answer

Oxygen, Carbon, Hydrogen, Nitrogen

Question 3

A compound is defined as:

Accepted Answer

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

Question 4

If an atom has an atomic number of 7 and a mass number of 15, how many neutrons does it have?

Accepted Answer

$$15 - 7 = 8$$

Question 5

Which statement about isotopes is correct?

Accepted Answer

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

Question 6

Carbon-14 has a half-life of 5700 years. If a fossil originally contained 100 grams of Carbon-14, how much would remain after 11,400 years?

Accepted Answer

$$100 \div 2 \div 2 = 25$$ grams

Question 7

Which of the following best explains why sodium (Na) and chlorine (Cl) form an ionic bond?

Accepted Answer

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

Question 8

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

Accepted Answer

Covalent bond

Question 9

What is the main reason water (H$$_2O) is a $$polar molecule?

Accepted Answer

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

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 property of water is primarily responsible for its ability to dissolve many ionic compounds?

Accepted Answer

Its polarity, which allows it to surround and separate ions.

Question 12

Which of the following is true about chemical reactions?

Accepted Answer

Chemical reactions involve the making and breaking of chemical bonds.

Question 13

If the atomic number of an atom is 12 and its mass number is 24, what is the number of neutrons?

Accepted Answer

$$24 - 12 = 12$$

Question 14

Which of the following best describes the concept of electronegativity?

Accepted Answer

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

Question 15

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

Accepted Answer

Using radioactive tracers to track atoms through metabolism in medical diagnostics.

Question 16

What is the main difference between a polar covalent bond and a nonpolar covalent bond?

Accepted Answer

Polar covalent bonds involve unequal sharing of electrons, while nonpolar covalent bonds involve equal sharing.

Question 17

Which of the following best explains why noble gases are chemically inert?

Accepted Answer

They have a full valence shell of electrons.

Question 18

Which of the following is an example of a chemical reaction that is essential for life?

Accepted Answer

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

Question 19

Which of the following best describes chemical equilibrium?

Accepted Answer

The forward and reverse reactions occur at the same rate, and the concentrations of reactants and products remain constant.

Question 20

Which type of interaction allows a gecko to climb smooth surfaces?

Accepted Answer

Van der Waals interactions

Chapter 2: The Chemical Context of Life – General Biology Study Notes

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