Q: A solution has a pH of 5. What is the [H$$^+$$] concentration?

$$1 \times 10$$^{-5}$$\ \mathrm{M}$$

Question 1

Which property of water allows ice to float on liquid water, and why is this important for aquatic life in cold climates?

Accepted Answer

Water's expansion upon freezing; ice is less dense than liquid water, so it floats and insulates the water below.

Question 2

A spider is able to walk on the surface of a pond without sinking. Which property of water is primarily responsible for this phenomenon?

Accepted Answer

High surface tension due to cohesion among water molecules

Question 3

Which of the following best explains why coastal cities like Los Angeles have milder temperatures compared to inland cities like Riverside?

Accepted Answer

Water's high specific heat moderates temperature changes near the ocean.

Question 4

What is the molarity of a solution prepared by dissolving 42.23 g of NH$$_4Cl ($$molecular mass = 53.5 g/mol) in enough water to make 500.0 mL of solution?

Accepted Answer

$$0.791\ \mathrm{M}$$

Question 5

Which of the following substances would NOT dissolve well in water?

Accepted Answer

Vegetable oil (a lipid)

Question 6

Why does sweating help cool the human body?

Accepted Answer

Sweat absorbs heat as it evaporates, removing energy from the body.

Question 7

Which of the following equations correctly represents the dissociation of a strong acid in water?

Accepted Answer

$$\mathrm{HCl} + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{H}^+ + \mathrm{Cl}^-$$

Question 8

Calculate the pH of a solution with a hydrogen ion concentration of $$[\mathrm{H}^+] = 2.5 	imes 10$$^{-4}$$\ \mathrm{M}.$$

Accepted Answer

$$pH = 3.60$$

Question 9

Which of the following best describes a buffer?

Accepted Answer

A substance that minimizes changes in pH by reversibly binding H$$^+$$ ions.

Question 10

A solution is created by mixing $$3.60 	imes 10$$^{-3}$$ moles of NaOH and 5.95$$ 	imes $$10^{-4}$$ moles of HCl in 1.00 L of water. What is the pH of the resulting solution?

Accepted Answer

$$pH = 11.479$$

Question 11

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

Accepted Answer

Hydrogen bonds form between the hydrogen atom of one water molecule and the oxygen atom of another.

Question 12

What is the molecular mass of glucose (C$$_6H$_{12}O$_6$$)? (C = 12 g/mol, H = 1 g/mol, O = 16 g/mol)

Accepted Answer

$$180\ \mathrm{g/mol}$$

Question 13

Which of the following best explains why water is an excellent solvent for ionic compounds?

Accepted Answer

Water molecules are polar and form hydration shells around ions.

Question 14

Which of the following is a hydrophobic substance?

Accepted Answer

Olive oil

Question 15

If you have 1 mole of NaCl in 0.5 liters of water, what is the molarity of the solution?

Accepted Answer

$$2\ \mathrm{M}$$

Question 16

Which property of water is most important for the movement of water from the roots to the leaves in tall trees?

Accepted Answer

Cohesion and adhesion

Question 17

Which of the following best describes the relationship between pH and [H$$^+$$] in an aqueous solution?

Accepted Answer

$$pH = -\log [\mathrm{H}^+]$$

Question 18

Which of the following is NOT an emergent property of water that contributes to Earth's suitability for life?

Accepted Answer

High density as a solid

Question 19

A solution has a pH of 5. What is the [H$$^+$$] concentration?

Accepted Answer

$$1 	imes 10$$^{-5}$$\ \mathrm{M}$$

Water and Life: Properties, Structure, and Biological Importance

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