Question 1

Which of the following statements best describes an isotope of an element?

Accepted Answer

An atom with the same number of protons but a different number of neutrons.

Question 2

A neutral atom of sodium has an atomic number of 11 and a mass number of 23. How many neutrons does it have?

Accepted Answer

$$23 - 11 = 12$$ neutrons

Question 3

Which of the following elements is NOT one of the four most abundant elements in living matter?

Accepted Answer

Calcium

Question 4

What type of chemical bond is formed when one atom donates an electron to another atom, resulting in oppositely charged ions that attract each other?

Accepted Answer

Ionic bond

Question 5

Which statement about electron shells is correct?

Accepted Answer

Atoms are most stable when their outermost shell is filled.

Question 6

A radioactive isotope is useful in medical imaging because:

Accepted Answer

It emits energy that can be detected to track biological processes.

Question 7

Which of the following best explains why water molecules are polar?

Accepted Answer

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

Question 8

Which of the following is a consequence of the three-dimensional shape of biological molecules?

Accepted Answer

Molecules can recognize and interact with specific targets, such as receptors.

Question 9

Which equation correctly represents the formation of water from its elements?

Accepted Answer

$$2H_2 + O_2$ \rightarrow 2H_2O$$

Question 10

Which of the following best describes a hydrogen bond?

Accepted Answer

A bond formed when a hydrogen atom covalently bonded to one electronegative atom is attracted to another electronegative atom.

Question 11

If an atom has 8 protons, 8 neutrons, and 10 electrons, what is its charge?

Accepted Answer

$$8 - 10 = -2 ($$charge of -2)

Question 12

Which of the following is an example of a chemical reaction that is biologically important and reversible?

Accepted Answer

$$3H_2 + N_2$ \rightleftharpoons 2NH_3$$

Question 13

Which of the following best describes the difference between a compound and an element?

Accepted Answer

A compound consists of two or more elements in a fixed ratio, while an element cannot be broken down by chemical means.

Question 14

Which of the following is a trace element required by humans for normal thyroid function?

Accepted Answer

Iodine

Question 15

Which of the following best describes the role of endorphins in the human body?

Accepted Answer

They bind to opioid receptors to regulate pain and emotion.

Question 16

Which of the following is true about chemical equilibrium in a reaction?

Accepted Answer

The forward and reverse reactions occur at the same rate.

Question 17

Which of the following is a correct statement about oxidation and reduction reactions (redox reactions) in biological systems?

Accepted Answer

Oxidation involves the loss of electrons, while reduction involves the gain of electrons.

Question 18

Which of the following best explains why morphine can mimic the effects of endorphins in the brain?

Accepted Answer

Morphine has a similar molecular shape to endorphins, allowing it to bind to the same receptors.

Question 19

Which of the following is the correct formula for calculating the number of neutrons in an atom?

Accepted Answer

$$	ext{Number of neutrons} = 	ext{Mass number} - 	ext{Atomic number}$$

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

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