Question 1

Which property of water is primarily responsible for its ability to dissolve ionic and polar substances, making it an efficient solvent in biological systems?

Accepted Answer

Its polarity and ability to form hydrogen bonds

Question 2

A molecule of methane ($$CH_4) $$has which of the following molecular geometries, and what causes this shape?

Accepted Answer

Tetrahedral, due to repulsive forces between electron pairs

Question 3

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

Accepted Answer

Hydrogen bonds in ice create a lattice structure that is less dense than liquid water

Question 4

If the pH of a solution changes from 7 to 5, what happens to the concentration of hydrogen ions ($$[H^+]$$)?

Accepted Answer

It increases by a factor of 100

Question 5

Which of the following molecules is most likely to be hydrophobic?

Accepted Answer

Methane ($$CH_4)$$

Question 6

What is the main function of buffers in biological systems?

Accepted Answer

To maintain a relatively constant pH by accepting or donating $$H^+$$ ions

Question 7

Which statement correctly describes the relationship between valence electrons and chemical bonding?

Accepted Answer

Unpaired electrons in the valence shell participate in covalent bonding

Question 8

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

Accepted Answer

Cohesion is the attraction between water molecules; adhesion is the attraction between water and other substances

Question 9

Which molecule has a bent geometry due to unshared electron pairs on its central atom?

Accepted Answer

Water ($$H_2O)$$

Question 10

Which of the following chemical reactions is an example of catabolism?

Accepted Answer

Breakdown of glucose into carbon dioxide and water

Question 11

Why does water have a high specific heat compared to other substances?

Accepted Answer

Because extensive hydrogen bonding requires more energy to change temperature

Question 12

Which of the following best explains why proteins can maintain their three-dimensional shape in aqueous environments?

Accepted Answer

Hydrogen bonds between polar regions of proteins and water molecules

Question 13

A solution has a pH of 3. Which of the following statements is true?

Accepted Answer

It is acidic and contains a higher concentration of $$H^+$$ ions than pure water

Question 14

Which of the following molecules is most likely to form triple covalent bonds?

Accepted Answer

Molecular nitrogen ($$N_2)$$

Question 15

Which of the following is a consequence of water’s high heat of vaporization for living organisms?

Accepted Answer

It enables evaporative cooling, helping organisms regulate body temperature

Question 16

Which of the following best describes the role of activation energy in chemical reactions?

Accepted Answer

It is the energy required to break existing bonds and initiate a reaction

Question 17

Which of the following elements has four unpaired electrons in its valence shell, making it highly versatile in forming covalent bonds?

Accepted Answer

Carbon

Question 18

Which of the following best explains why hydrophobic molecules do not dissolve in water?

Accepted Answer

They are nonpolar and do not form hydrogen bonds with water

Question 19

Which of the following is true about chemical equilibrium in biological systems?

Accepted Answer

The rates of the forward and reverse reactions are equal

Question 20

Which of the following best describes the difference between acids and bases in aqueous solutions?

Accepted Answer

Acids donate protons and raise hydronium ion concentration; bases acquire protons and lower hydronium ion concentration

Chemistry and the Evolution of Life: Atoms, Molecules, and Water

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