Question 1

Which of the following statements best explains why water is an effective temperature buffer in living organisms?

Accepted Answer

Water has a high specific heat, meaning it can absorb or release large amounts of heat with only a slight change in its own temperature.

Question 2

A solution has a hydrogen ion concentration of $$[H^+] = 1 	imes 10$$^{-9}$$ \ \mathrm{M}. $$What is the pH of this solution?

Accepted Answer

$$9$$

Question 3

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 4

A sodium atom (Na) loses one electron to become a sodium ion (Na$$^+). $$What type of bond is most likely to form between Na$$^+$$ and Cl$$^- in $$table salt (NaCl)?

Accepted Answer

Ionic bond

Question 5

Which property of water allows insects to walk on its surface without sinking?

Accepted Answer

Surface tension

Question 6

A molecule of methane (CH$$_4) $$contains only single covalent bonds. Which statement about these bonds is correct?

Accepted Answer

Each single covalent bond involves the sharing of one pair of electrons between two atoms.

Question 7

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

Accepted Answer

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

Question 8

A buffer solution is added to a beaker of pure water. Which of the following best describes the function of the buffer if a strong acid is then added?

Accepted Answer

The buffer will accept excess $$H^+$$ ions, minimizing the change in pH.

Question 9

Which of the following is true regarding hydrophilic and hydrophobic substances?

Accepted Answer

Hydrophilic substances have an affinity for water and dissolve easily in it.

Question 10

A solution contains $$0.5$$ moles of glucose dissolved in $$1$$ liter of water. What is the molarity of the solution?

Accepted Answer

$$0.5 \ \mathrm{M}$$

Question 11

Which of the following best describes a polar covalent bond?

Accepted Answer

A covalent bond in which the sharing of the electron pair is unequal, resulting in partial charges on the atoms.

Question 12

If the pH of a solution changes from $$6 to$$ $$4$$, what happens to the hydrogen ion concentration?

Accepted Answer

It increases by a factor of $$100.$$

Question 13

Which of the following is a correct statement about acids and bases?

Accepted Answer

An acid increases the concentration of $$H^+$$ ions in a solution.

Question 14

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

Accepted Answer

Water is a polar molecule, so its partial charges surround and separate the Na$$^+$$ and Cl$$^-$$ ions.

Question 15

Which of the following is the best example of a mixture?

Accepted Answer

Air, which contains nitrogen, oxygen, carbon dioxide, and other gases in variable ratios.

Question 16

Which of the following best describes the function of hydrogen bonds in biological molecules?

Accepted Answer

They help stabilize the three-dimensional shape of large molecules such as proteins and DNA.

Question 17

A molecule has a molecular weight of $$180 \ \mathrm{g/mol}. $$How many grams are needed to make $$2$$ moles of this molecule?

Accepted Answer

$$360 \ \mathrm{g}$$

Question 18

Which of the following statements about electron shells is correct?

Accepted Answer

Electrons in shells farther from the nucleus have higher energy levels.

Question 19

Which of the following best describes a cation?

Accepted Answer

A positively charged atom or molecule.

Question 20

A scientist adds a strong base to a solution, causing the pH to rise from $$7 to$$ $$9. $$What happens to the $$[H^+]$$ concentration?

Accepted Answer

It decreases by a factor of $$100.$$

Atoms, Molecules, and Life: Foundations of Biological Chemistry

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