Question 1

Which of the following best describes a compound?

Accepted Answer

A substance consisting of two or more different elements combined in a fixed ratio.

Question 2

Which statement about isotopes is correct?

Accepted Answer

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

Question 3

A neutral atom of sodium (Na) 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 4

Which of the following best explains why water is considered a polar molecule?

Accepted Answer

It contains polar covalent bonds and has an unequal distribution of charges in different regions of the molecule.

Question 5

Which type of chemical bond is responsible for the attraction between the slightly positive hydrogen atom of one water molecule and the slightly negative oxygen atom of another water molecule?

Accepted Answer

Hydrogen bond

Question 6

A molecule of oxygen gas ($$O_2) is $$held together by which type of bond?

Accepted Answer

Nonpolar covalent bond

Question 7

Which of the following statements about trace elements is true?

Accepted Answer

They are required in minute quantities but are essential for life.

Question 8

If an atom has 17 protons, 18 neutrons, and 17 electrons, what is its atomic mass?

Accepted Answer

$$17 + 18 = 35$$

Question 9

Which of the following best describes an ionic bond?

Accepted Answer

A chemical bond resulting from the attraction between oppositely charged ions.

Question 10

A student dissolves table salt (NaCl) in water. Which of the following best describes the interaction between NaCl and water molecules?

Accepted Answer

The positive sodium ions are attracted to the negative oxygen ends of water molecules, and the negative chloride ions are attracted to the positive hydrogen ends.

Question 11

Which of the following is a real-life example of cohesion?

Accepted Answer

Water droplets forming beads on a car windshield due to hydrogen bonding between water molecules.

Question 12

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

Accepted Answer

Hydrogen bonds hold water molecules in ice farther apart, making ice less dense than liquid water.

Question 13

A radioactive isotope of carbon, $$^{14}C$$, is used in medical imaging. What makes $$^{14}C$$ different from the most common carbon isotope, $$^{12}C$$?

Accepted Answer

$$^{14}C$$ has two more neutrons than $$^{12}C.$$

Question 14

Which of the following best describes the role of electronegativity in the formation of polar covalent bonds?

Accepted Answer

Electronegativity differences cause shared electrons to be pulled closer to one atom, creating partial charges.

Question 15

Which of the following is the best example of a chemical reaction?

Accepted Answer

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

Question 16

A molecule of methane ($$CH_4) is $$held together by which type of bond?

Accepted Answer

Nonpolar covalent bonds

Question 17

Which of the following best describes the difference between adhesion and cohesion?

Accepted Answer

Cohesion is the attraction between molecules of the same kind, while adhesion is the attraction between different kinds of molecules.

Question 18

Which of the following best explains why salt (NaCl) is classified as an ionic compound?

Accepted Answer

It is formed by the transfer of electrons from sodium to chlorine, resulting in oppositely charged ions.

Question 19

A scientist is studying a molecule that has regions of partial positive and partial negative charge. Which type of bond is most likely responsible for this property?

Accepted Answer

Polar covalent bond

Question 20

Which of the following best describes the relationship between atomic number and atomic mass?

Accepted Answer

Atomic number is the number of protons, while atomic mass is the sum of protons and neutrons.

Fundamentals of Matter and Chemical Bonds in Biology

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