Question 1

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

Accepted Answer

A molecule consists of two or more atoms of the same element, while a compound consists of atoms of different elements bonded together.

Question 2

Which element makes up the largest percentage of human body weight, including water?

Accepted Answer

Oxygen

Question 3

An atom of sodium (Na) has 11 protons, 12 neutrons, and 10 electrons. What is its charge and classification?

Accepted Answer

It is a cation with a charge of $$+1.$$

Question 4

Which type of chemical bond is responsible for the cohesion of water molecules?

Accepted Answer

Hydrogen bonds

Question 5

A solution has a pH of 4. Which of the following statements is true?

Accepted Answer

The concentration of $$[H^+] is $$higher than $$[OH^-].$$

Question 6

Which of the following best explains why ice floats on water?

Accepted Answer

Hydrogen bonds in ice create a lattice structure that makes ice less dense than liquid water.

Question 7

Which of the following is a trace element in the human body?

Accepted Answer

Zinc

Question 8

A radioactive isotope of carbon, $$^{14}C$$, is used in medical imaging. What makes it radioactive?

Accepted Answer

It has an unstable nucleus due to extra neutrons.

Question 9

Which of the following best describes a buffer in biological systems?

Accepted Answer

A buffer resists changes in pH by absorbing or releasing $$H^+ or$$ $$OH^-$$ ions.

Question 10

Which of the following scenarios demonstrates a reductionist approach in biology?

Accepted Answer

Investigating the function of a single enzyme in a metabolic pathway.

Question 11

Which of the following is true about the atomic number of an element?

Accepted Answer

It is equal to the number of protons in the atom.

Question 12

Which of the following chemical reactions is reversible and can reach equilibrium?

Accepted Answer

$$A + B \rightleftharpoons C$$

Question 13

Which property of water allows it to dissolve many ionic compounds, such as NaCl?

Accepted Answer

Its polarity and ability to form hydrogen bonds

Question 14

A molecule of ammonia ($$NH_3) $$acts as a base in water. What does it do?

Accepted Answer

It absorbs $$H^+$$ ions.

Question 15

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

Accepted Answer

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

Question 16

Which of the following statements about electron shells is correct?

Accepted Answer

The outermost shell is called the valence shell and determines chemical reactivity.

Question 17

Which of the following is an example of a polar covalent bond?

Accepted Answer

The bond between oxygen and hydrogen in a water molecule ($$H_2O)$$

Question 18

If a solution has a $$[H^+]$$ concentration of $$1 	imes 10$$^{-7}$$ M, what is its pH?

Accepted Answer

$$pH = 7$$

Question 19

Which of the following best describes van der Waals interactions?

Accepted Answer

Weak attractions between molecules due to temporary charge fluctuations.

Question 20

Which of the following would most likely disrupt the function of a biological buffer system in human blood?

Accepted Answer

A rapid addition of a strong acid or base.

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

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