Q: If the [OH$$^-$$] of a solution is $$1 \times 10$$^{-9}$$ M, what is the [H$$^+$$] and the pH of the solution?

[H$$^+$$] = $$1 \times 10$$^{-5}$$ M, pH = 5

Question 1

Which property of water is primarily responsible for the ability of some insects to walk on water surfaces without sinking?

Accepted Answer

Cohesion due to hydrogen bonding

Question 2

Why does ice float on liquid water, and why is this important for aquatic life?

Accepted Answer

Ice is less dense than liquid water due to the hydrogen bonds forming a crystalline structure, allowing it to float and insulate the water below.

Question 3

A solution has a hydrogen ion concentration of $$1 	imes 10$$^{-4}$$ M. What is its pH?

Accepted Answer

$$4$$

Question 4

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

Accepted Answer

Water molecules are polar, allowing them to surround and separate ions and polar molecules.

Question 5

If the [OH$$^-$$] of a solution is $$1 	imes 10$$^{-9}$$ M, what is the [H$$^+$$] and the pH of the solution?

Accepted Answer

[H$$^+$$] = $$1 	imes 10$$^{-5}$$ M, pH = 5

Question 6

Which of the following changes would make water a nonpolar molecule?

Accepted Answer

Make water a linear molecule.

Question 7

A beaker contains 1 liter of a 2 M sucrose solution. How many grams of sucrose (C$$_{12}H$_{22}O$_{11}$$, molar mass = 342 g/mol) are present?

Accepted Answer

684 g

Question 8

Which of the following best describes the role of buffers in biological systems?

Accepted Answer

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

Question 9

Why does sweating help cool the human body?

Accepted Answer

Sweat absorbs heat as it evaporates, removing energy from the body due to water's high heat of vaporization.

Question 10

Which of the following statements about hydrogen bonds in water is correct?

Accepted Answer

Hydrogen bonds are weak, short-lived, but numerous, giving water its unique properties.

Question 11

A plant is able to transport water from its roots to its leaves against gravity. Which property of water is most directly responsible for this phenomenon?

Accepted Answer

Cohesion and adhesion due to hydrogen bonding

Question 12

If a solution has a pH of 3, how many times more acidic is it than a solution with a pH of 6?

Accepted Answer

1000 times

Question 13

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

Accepted Answer

Hydrogen bonds between water molecules require a large amount of energy to break.

Question 14

What is the molarity of a solution containing 0.5 moles of NaCl dissolved in 250 mL of water?

Accepted Answer

0.2 M

Question 15

Which of the following is an example of adhesion?

Accepted Answer

Water molecules forming hydrogen bonds with plant cell walls

Question 16

A solution has a [H$$^+$$] of $$1 	imes 10$$^{-7}$$ M. What is the [OH$$^-$$] in this solution?

Accepted Answer

$$1 	imes 10$$^{-7}$$ M

Question 17

Which of the following substances would be considered hydrophobic?

Accepted Answer

A molecule with many nonpolar covalent bonds, such as C-H

Question 18

If you add a strong acid to a buffered solution, what will most likely happen to the pH?

Accepted Answer

The pH will remain relatively constant.

Question 19

Which of the following best describes the relationship between [H$$^+$$] and [OH$$^-$$] in pure water at 25°C?

Accepted Answer

[H$$^+$$] equals [OH$$^-$$], both at $$1 	imes 10$$^{-7}$$ M

Question 20

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

Accepted Answer

Evaporation of water from surfaces cools organisms efficiently.

Water and Life: Properties, Structure, and Biological Importance

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