Question 1

Which of the following statements best explains why atoms are electrically neutral under normal conditions?

Accepted Answer

Atoms have an equal number of protons and electrons, so their charges balance.

Question 2

A radioactive isotope of carbon, $$^{14}C$$, is used in dating ancient biological materials. What property of $$^{14}C$$ makes it useful for this purpose?

Accepted Answer

$$^{14}C$$ decays at a predictable rate, allowing scientists to estimate the age of a sample based on the remaining amount.

Question 3

Which of the following best describes a covalent bond?

Accepted Answer

A type of strong chemical bond in which two atoms share one or more pairs of valence electrons.

Question 4

If an atom has an atomic number of 17 and a mass number of 35, how many neutrons does it have?

Accepted Answer

$$35 - 17 = 18$$ neutrons

Question 5

Which of the following is a property of water that results from hydrogen bonding?

Accepted Answer

High surface tension

Question 6

A sodium atom (Na) has an atomic number of 11. When it forms an ionic bond with chlorine (Cl), what happens to the sodium atom?

Accepted Answer

It loses one electron and becomes a positively charged ion ($$Na^+).$$

Question 7

Which of the following best describes the Law of Conservation of Energy?

Accepted Answer

Energy cannot be created or destroyed, only transformed from one form to another.

Question 8

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

Accepted Answer

The rate of the forward reaction equals the rate of the reverse reaction.

Question 9

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

Accepted Answer

Calcium (Ca)

Question 10

A molecule of methane ($$CH_4) is $$described as nonpolar. What does this mean about the distribution of electrons in the molecule?

Accepted Answer

Electrons are shared equally between the carbon and hydrogen atoms.

Question 11

Which of the following best explains why water is an excellent solvent for ionic compounds?

Accepted Answer

Water is a polar molecule, so it can surround and separate positive and negative ions.

Question 12

Which of the following is a trace element required by humans?

Accepted Answer

Iodine (I)

Question 13

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

Accepted Answer

A molecule consists of two or more atoms held together by chemical bonds, while a compound contains at least two different elements.

Question 14

Which of the following best explains why geckos can climb walls?

Accepted Answer

They use van der Waals interactions between their feet and the wall surface.

Question 15

If a chemical reaction is at dynamic equilibrium, which of the following is true?

Accepted Answer

The rates of the forward and reverse reactions are equal, but the reaction is still occurring.

Question 16

Which of the following best describes the role of surfactant in the lungs of newborns?

Accepted Answer

It reduces surface tension, preventing alveoli from collapsing.

Question 17

Which of the following is true about the energy levels of electrons in an atom?

Accepted Answer

Electrons further from the nucleus have higher energy.

Question 18

Which of the following best describes electronegativity?

Accepted Answer

The attraction of a given atom for the electrons in a covalent bond.

Question 19

Which of the following is a correct statement about isotopes?

Accepted Answer

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

Question 20

Which of the following best explains why partial charges are critical in biology?

Accepted Answer

They allow molecules like water to form hydrogen bonds, which are essential for many biological processes.

General Biology: Chemical Context of Life and Properties of Water

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