$$\text{Atomic mass} = \text{Number of protons} + \text{Number of neutrons}$$

Question 1

Which of the following statements best explains why living organisms are subject to the basic laws of physics and chemistry?

Accepted Answer

Because all living organisms are composed of matter, which obeys physical and chemical laws.

Question 2

Which of the following is NOT a subatomic particle found in atoms?

Accepted Answer

Ion

Question 3

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 4

Which equation correctly represents the calculation of atomic mass for an atom?

Accepted Answer

$$	ext{Atomic mass} = 	ext{Number of protons} + 	ext{Number of neutrons}$$

Question 5

Radioactive isotopes are useful in medicine because:

Accepted Answer

They can be used to diagnose medical disorders by tracing metabolic processes.

Question 6

Which of the following best describes a covalent bond?

Accepted Answer

The sharing of a pair of valence electrons between two atoms.

Question 7

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 8

Which of the following elements is NOT one of the four major elements that make up 96% of living matter?

Accepted Answer

Calcium

Question 9

If an atom has a full valence shell, how does this affect its chemical reactivity?

Accepted Answer

It is chemically inert and unlikely to form bonds.

Question 10

Which of the following best describes the role of electronegativity in a covalent bond?

Accepted Answer

Electronegativity determines how strongly an atom pulls shared electrons toward itself.

Question 11

Which of the following is a correct example of an ionic bond?

Accepted Answer

The transfer of an electron from sodium to chlorine to form sodium chloride ($$	ext{NaCl}).$$

Question 12

Which statement about hydrogen bonds is TRUE?

Accepted Answer

Hydrogen bonds form when a hydrogen atom covalently bonded to one electronegative atom is attracted to another electronegative atom.

Question 13

A molecule of water ($$	ext{H}_2	ext{O}) $$has a bent shape. What determines this molecular shape?

Accepted Answer

The positions of the atoms' nuclei and the orbitals occupied by electrons.

Question 14

Which of the following best describes a cation?

Accepted Answer

A positively charged ion.

Question 15

Which of the following is a trace element required by organisms in minute quantities?

Accepted Answer

Iron

Question 16

Which statement about electron orbitals is correct?

Accepted Answer

An orbital is a three-dimensional space where an electron is found 90% of the time.

Question 17

Which of the following best explains why weak chemical bonds are important in biological systems?

Accepted Answer

They allow large molecules to interact and form temporary associations necessary for biological function.

Question 18

A molecule has the formula $$	ext{CH}_4. $$What type of covalent bond is present between the carbon and hydrogen atoms?

Accepted Answer

Nonpolar covalent bond

Question 19

Which of the following best describes the relationship between molecular shape and function?

Accepted Answer

The shape of a molecule determines how it interacts with other molecules and its biological function.

Question 20

Which of the following is the correct definition of a compound?

Accepted Answer

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

The Chemical Context of Life: Foundations for General Biology

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