Question 1

Which of the following statements best explains why water (H$$_2O) $$molecules can form hydrogen bonds with each other?

Accepted Answer

The oxygen atom in water is more electronegative than hydrogen, creating a partial negative charge on oxygen and a partial positive charge on hydrogen.

Question 2

A radioactive isotope of carbon, $$^{14}C$$, decays into nitrogen-14 ($$^{14}N) by $$beta decay. Which subatomic particle changes during this process?

Accepted Answer

A neutron becomes a proton.

Question 3

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

Accepted Answer

A compound is a molecule composed of atoms of two or more different elements, while a molecule can be composed of the same or different elements.

Question 4

Which of the following elements is NOT one of the four most abundant elements in living organisms by weight?

Accepted Answer

Calcium

Question 5

A sodium atom (Na) loses one electron to become a sodium ion (Na$$^+). $$What type of bond can it now form with a chloride ion (Cl$$^-$$)?

Accepted Answer

Ionic bond

Question 6

Which of the following best explains why carbon is able to form such a wide variety of molecules?

Accepted Answer

Carbon can form up to four covalent bonds with other atoms.

Question 7

If an atom has an atomic number of 8 and a mass number of 18, how many neutrons does it have?

Accepted Answer

10

Question 8

Which of the following scenarios best illustrates a chemical reaction?

Accepted Answer

Hydrogen gas and oxygen gas combining to form water: $$2H_2 + O_2$ \rightarrow 2H_2O$$

Question 9

Which of the following best describes a polar covalent bond?

Accepted Answer

Electrons are shared unequally, resulting in partial charges on the atoms.

Question 10

A patient is injected with a radioactive isotope for medical imaging. Which property of isotopes makes this possible?

Accepted Answer

Isotopes have different numbers of neutrons, which can make them unstable and radioactive.

Question 11

Which of the following best explains why table salt (NaCl) dissolves easily in water?

Accepted Answer

The polar water molecules surround and separate the Na$$^+$$ and Cl$$^-$$ ions.

Question 12

Which of the following is true about the electron distribution in atoms and its effect on chemical bonding?

Accepted Answer

Atoms with incomplete outer shells tend to form bonds to achieve stability.

Question 13

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

Accepted Answer

The bond between two hydrogen atoms in H$$_2.$$

Question 14

A molecule of ammonia (NH$$_3) $$can form hydrogen bonds with water molecules. Which property of ammonia allows this?

Accepted Answer

Ammonia has a partially negative nitrogen atom and partially positive hydrogen atoms.

Question 15

Which of the following best describes the relationship between atomic number and the identity of an element?

Accepted Answer

The atomic number is the number of protons, which determines the element.

Question 16

Which of the following best explains why isotopes of the same element have nearly identical chemical properties?

Accepted Answer

They have the same number of protons and electrons.

Question 17

Which of the following is a real-life example of a decomposition reaction?

Accepted Answer

Digestion of hydrogen peroxide by catalase: $$2H_2O_2 \rightarrow 2H_2O + O_2$

Question 18

Which of the following best describes a cation?

Accepted Answer

An atom that has lost electrons and is positively charged.

Question 19

Which of the following best explains why noble gases (such as helium and neon) are chemically inert?

Accepted Answer

They have full outer electron shells, making them stable and unlikely to form bonds.

Question 20

Which of the following is the correct formula for calculating the atomic mass of an atom?

Accepted Answer

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

The Chemical Context of Life: Foundations for General Biology

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