Question 1

Which of the following best explains why water is less dense as a solid (ice) than as a liquid?

Accepted Answer

Hydrogen bonds in ice form a lattice structure that spaces water molecules farther apart than in liquid water.

Question 2

A scientist adds a substance to water and observes that the pH decreases from 7 to 4. Which of the following best describes the substance added?

Accepted Answer

An acid, because it increases the concentration of $$\mathrm{H^+}$$ ions in solution.

Question 3

Which of the following best describes a covalent bond?

Accepted Answer

A bond where atoms share pairs of electrons.

Question 4

Which property of water allows it to move upward through the stem of a plant against gravity?

Accepted Answer

Cohesion and adhesion, due to hydrogen bonding between water molecules and plant cell walls.

Question 5

Which of the following statements about hydrogen bonds is correct?

Accepted Answer

Hydrogen bonds are weak individually but collectively contribute to important properties of water.

Question 6

A molecule of sodium chloride ($$\mathrm{NaCl}) $$forms when sodium donates an electron to chlorine. What type of bond is formed between sodium and chlorine?

Accepted Answer

Ionic bond

Question 7

Which of the following best explains why water has a high specific heat?

Accepted Answer

Hydrogen bonds between water molecules absorb heat when they break and release heat when they form.

Question 8

Which of the following is true regarding the octet rule and chemical reactivity?

Accepted Answer

Atoms tend to gain, lose, or share electrons to achieve a full outer shell of 8 electrons.

Question 9

A solution has a pH of 9. Which of the following statements is correct?

Accepted Answer

The solution is basic and has a lower concentration of $$\mathrm{H^+}$$ ions than pure water.

Question 10

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

Accepted Answer

Polar covalent bonds involve unequal sharing of electrons, resulting in partial charges; nonpolar covalent bonds involve equal sharing of electrons.

Question 11

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

Accepted Answer

Water droplets sticking to the surface of a leaf after rain.

Question 12

Which of the following is a direct consequence of water's polarity?

Accepted Answer

Water can dissolve many ionic and polar substances.

Question 13

A biologist is studying a molecule that has 11 electrons: 2 in the first shell, 8 in the second shell, and 1 in the third shell. Which element is this most likely to be?

Accepted Answer

Sodium ($$\mathrm{Na})$$

Question 14

Which of the following best explains why sweating helps cool the human body?

Accepted Answer

Evaporation of water from the skin absorbs heat due to water's high heat of vaporization.

Question 15

Which of the following is NOT a property of water that is important for life?

Accepted Answer

Water molecules are nonpolar and do not interact with ions.

Question 16

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 17

A molecule contains a polar covalent bond. Which of the following is most likely true about this molecule?

Accepted Answer

It has regions of partial positive and partial negative charge.

Question 18

Which of the following best explains why salt ($$\mathrm{NaCl}) $$dissolves easily in water?

Accepted Answer

Water's polarity allows it to surround and separate the positive and negative ions.

Question 19

Which of the following is the best example of a hydrogen bond in a biological context?

Accepted Answer

The attraction between the hydrogen of one water molecule and the oxygen of another water molecule.

Question 20

A solution has a $$[\mathrm{H^+}]$$ concentration of $$1 	imes 10$$^{-5}$$ M. What is the pH of this solution?

Accepted Answer

$$5$$

Water and Carbon: The Chemical Basis of Life – Study Notes

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