Q: Which equation correctly represents the calculation of an atom's mass number?

$\text{Mass number} = \text{Number of protons} + \text{Number of neutrons}$

Question 1

Which of the following statements best explains why water has a high specific heat compared to other molecules?

Accepted Answer

Water molecules have extensive hydrogen bonding, so energy input is used to break many weak hydrogen bonds before increasing temperature.

Question 2

An atom of carbon has 6 protons, 6 neutrons, and 6 electrons. What is its atomic number and mass number?

Accepted Answer

Atomic number: $6$, Mass number: $12$

Question 3

Which of the following best describes the difference between polar and nonpolar covalent bonds?

Accepted Answer

Polar covalent bonds involve unequal sharing of electrons due to differences in electronegativity, while nonpolar covalent bonds involve equal sharing.

Question 4

Which property of water is most directly responsible for its ability to dissolve ionic compounds like NaCl?

Accepted Answer

Water's polarity, allowing it to surround and separate ions

Question 5

If an atom has a full valence shell, what is its chemical reactivity likely to be?

Accepted Answer

It will be very stable and unlikely to react.

Question 6

Which of the following best describes the formation of an ionic bond between sodium (Na) and chlorine (Cl)?

Accepted Answer

Sodium donates an electron to chlorine, resulting in oppositely charged ions that attract each other.

Question 7

Which equation correctly represents the calculation of an atom's mass number?

Accepted Answer

$	ext{Mass number} = 	ext{Number of protons} + 	ext{Number of neutrons}$

Question 8

A molecule of water ($\mathrm{H_2O}$) is described as polar. What does this mean in terms of electron distribution?

Accepted Answer

Electrons are shared unequally, with oxygen having a partial negative charge and hydrogen a partial positive charge.

Question 9

Which of the following scenarios best illustrates the concept of electronegativity?

Accepted Answer

A fluorine atom attracts shared electrons more strongly than a hydrogen atom in a covalent bond.

Question 10

Why does sweating help cool the body, in terms of water's properties?

Accepted Answer

Evaporation of sweat requires energy to break hydrogen bonds, removing heat from the skin due to water's high heat of vaporization.

Question 11

Which of the following best explains why noble gases like argon are chemically inert?

Accepted Answer

Their outer electron shells are full, so they do not need to gain, lose, or share electrons.

Question 12

Which of the following molecules would you expect to be hydrophobic?

Accepted Answer

A molecule composed mostly of nonpolar covalent bonds, such as hydrocarbons

Question 13

Which of the following is a consequence of extensive hydrogen bonding in water for living cells?

Accepted Answer

Cells benefit from temperature stabilization due to water's high specific heat.

Question 14

Which of the following best describes the electron-sharing continuum in chemical bonds?

Accepted Answer

Electrons can be shared equally (nonpolar covalent), unequally (polar covalent), or transferred (ionic bonds).

Question 15

Which of the following statements about covalent bonds is correct?

Accepted Answer

Covalent bonds form when atoms share pairs of electrons to fill their valence shells.

Question 16

A molecule has the formula $\mathrm{C_2H_6}$ (ethane). What type of covalent bonds are present between the carbon and hydrogen atoms?

Accepted Answer

Nonpolar covalent bonds, because the electronegativity difference between C and H is small.

Question 17

Which of the following best explains why ethanol ($\mathrm{C_2H_5OH}$) has a lower specific heat than water?

Accepted Answer

Ethanol has fewer hydrogen bonds than water, so less energy is required to increase its temperature.

Question 18

Which of the following is true about the relationship between electronegativity and position on the periodic table?

Accepted Answer

Electronegativity increases as you move up and to the right.

Question 19

Which of the following best describes the role of water as a solvent in biological systems?

Accepted Answer

Water dissolves polar and ionic substances by surrounding them with partial charges.

Chapter 2: Chemistry Fundamentals for Cell & Molecular Biology

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