$$2 \times 1 + 1 \times 16 = 18 g/$$mol

Question 1

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

Accepted Answer

Hydrogen bonds in ice lock water molecules at a greater distance, making ice less dense than liquid water.

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 property of water allows it to moderate temperature in living organisms?

Accepted Answer

Water has a high specific heat, requiring more energy to change temperature.

Question 4

Which of the following best describes a covalent bond?

Accepted Answer

The sharing of pairs of valence electrons between two atoms.

Question 5

A radioactive isotope of carbon, carbon-14, is used in dating fossils. What makes carbon-14 different from carbon-12?

Accepted Answer

Carbon-14 has more neutrons than carbon-12.

Question 6

Which of the following is true about the pH scale?

Accepted Answer

A solution with $$[H^+] = 10$$^{-2}$$ is more acidic than a solution with $$[H^+] = $$10^{-6}.$$

Question 7

Which of the following best describes the role of buffers in biological systems?

Accepted Answer

Buffers minimize changes in pH by accepting or donating hydrogen ions.

Question 8

Which type of chemical bond is responsible for the unique properties of water, such as cohesion and surface tension?

Accepted Answer

Hydrogen bonds between water molecules.

Question 9

What is the molar mass of water ($$H_2O$$)?

Accepted Answer

$$2 	imes 1 + 1 	imes 16 = 18 g/$$mol

Question 10

Which of the following best describes an element?

Accepted Answer

A substance that cannot be broken down into other substances by chemical reactions.

Question 11

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 12

Which of the following is a consequence of water’s high heat of vaporization for living organisms?

Accepted Answer

Evaporation of water from skin cools the body by absorbing heat.

Question 13

Which of the following best describes a polar covalent bond?

Accepted Answer

Bonding electrons are shared unequally between two atoms.

Question 14

What is the main reason ionic compounds (salts) dissolve easily in water?

Accepted Answer

Water’s polar molecules are attracted to the charged ions, separating them.

Question 15

Which of the following is the correct formula for calculating pH?

Accepted Answer

$$pH = -\log [H^+]$$

Question 16

Which of the following is NOT a major role of buffers in the human body?

Accepted Answer

Increase the acidity of blood

Question 17

Which of the following best describes the octet rule?

Accepted Answer

Atoms tend to transfer or share electrons to achieve a stable configuration of 8 electrons in their outer shell.

Question 18

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

Accepted Answer

Tracking chemicals in the body for medical research.

Question 19

Which of the following best explains why water is a versatile solvent?

Accepted Answer

Water’s polar molecules are attracted to ions and polar substances.

The Chemical Context of Life: Foundations for General Biology

Study Guide - Practice Questions