$$pH = -\log_{10}(1 \times 10$$^{-5}$$) = 5$$

Question 1

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

Accepted Answer

Ice is less dense than liquid water because hydrogen bonds form a more open crystal structure in the solid state.

Question 2

Which property of water is primarily responsible for the movement of water from the roots to the leaves in plants?

Accepted Answer

Cohesion and adhesion, which allow water molecules to stick to each other and to the walls of plant vessels.

Question 3

A solution has a hydrogen ion concentration of $$1 	imes 10$$^{-5}$$ M. What is its pH?

Accepted Answer

$$pH = -\log_{10}(1 	imes 10$$^{-5}$$) = 5$$

Question 4

Which of the following best describes an ionic bond?

Accepted Answer

A bond formed by the complete transfer of one or more electrons from one atom to another, resulting in oppositely charged ions.

Question 5

Which of the following molecules would be least likely to dissolve in water?

Accepted Answer

A nonpolar molecule such as oil.

Question 6

What is the main reason water has a high specific heat compared to other substances?

Accepted Answer

Many hydrogen bonds must be broken for water molecules to move faster, requiring more energy.

Question 7

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 8

Which of the following best describes a polar covalent bond?

Accepted Answer

A bond in which electrons are shared unequally, resulting in partial charges on the atoms.

Question 9

Which of the following elements is the most electronegative?

Accepted Answer

Oxygen

Question 10

A buffer is important in biological systems because it:

Accepted Answer

Minimizes changes in pH when acids or bases are added.

Question 11

Which of the following is true about the structure of a water molecule?

Accepted Answer

It has a bent geometry and is polar due to the higher electronegativity of oxygen.

Question 12

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

Accepted Answer

The partial charges on water molecules surround and stabilize the Na+ and Cl- ions.

Question 13

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

Accepted Answer

Evaporation of sweat cools the body by absorbing large amounts of heat.

Question 14

Which of the following is the correct formula for calculating the pH of a solution?

Accepted Answer

$$pH = -\log_{10}[H^+]$$

Question 15

Which of the following best describes the difference between a molecule and a compound?

Accepted Answer

A molecule consists of two or more atoms held together by covalent bonds, while a compound consists of atoms of different elements.

Question 16

Which of the following is a real-world example of the hydrophobic effect?

Accepted Answer

Oil droplets clumping together in water.

Question 17

Which of the following best explains why water is an excellent solvent for polar and ionic substances?

Accepted Answer

Water’s polarity allows it to interact with and stabilize charged and polar molecules.

Question 18

Which of the following is a direct biological consequence of water’s high specific heat?

Accepted Answer

Organisms are protected from rapid temperature changes in their environment.

Question 19

Which of the following statements about hydrogen bonds is correct?

Accepted Answer

Hydrogen bonds are weak electrical attractions between the partial positive charge on hydrogen and the partial negative charge on another atom.

Water and Carbon: The Chemical Basis of Life – General Chemistry Foundations

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