$$[H^+] \times [OH^-] = 1 \times 10$$^{-14}$$

Question 1

Which part of a water molecule carries a partial negative charge, and why does this occur?

Accepted Answer

The oxygen atom, because it is more electronegative and pulls shared electrons closer.

Question 2

Which property of water allows insects to walk on its surface, and what molecular interaction is responsible for this?

Accepted Answer

Surface tension, due to hydrogen bonding among water molecules.

Question 3

A drop of water sticks to a glass window. Which property of water is primarily responsible for this phenomenon?

Accepted Answer

Adhesion

Question 4

Which equation correctly relates the concentration of hydrogen ions $$[H^+]$$ and hydroxide ions $$[OH^-] in $$pure water at 25°C?

Accepted Answer

$$[H^+] 	imes [OH^-] = 1 	imes 10$$^{-14}$$

Question 5

Why does ice float on liquid water?

Accepted Answer

Ice is less dense than liquid water because hydrogen bonds keep water molecules farther apart in solid form.

Question 6

Which of the following best describes a buffer in biological systems?

Accepted Answer

A solution that resists changes in pH when acids or bases are added.

Question 7

If the pH of a solution is 4, what is the concentration of hydrogen ions $$[H^+] in $$moles/liter?

Accepted Answer

$$[H^+] = 1 	imes 10$$^{-4}$$

Question 8

Which property of water is most important for moderating Earth's climate?

Accepted Answer

Its high specific heat due to hydrogen bonding.

Question 9

A solution has a pH of 8. Which of the following best describes this solution?

Accepted Answer

It is basic, with a low concentration of $$[H^+].$$

Question 10

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

Accepted Answer

Water molecules are polar and can form hydration shells around ions.

Question 11

Which of the following equations correctly defines pH?

Accepted Answer

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

Question 12

Which of the following is a real-world example of water's high heat of vaporization?

Accepted Answer

Sweating cools the human body as water evaporates from the skin.

Question 13

Which of the following best describes the role of bicarbonate ($$\mathrm{HCO}_3^-) in $$blood?

Accepted Answer

It acts as a buffer to maintain pH stability.

Question 14

A lake receives acid rain, lowering its pH from 7 to 5. By what factor has the hydrogen ion concentration increased?

Accepted Answer

100 times

Question 15

Which of the following best describes a hydrophobic substance?

Accepted Answer

It repels water and does not dissolve.

Question 16

Which of the following is NOT a property resulting from hydrogen bonding in water?

Accepted Answer

Water's ability to dissolve nonpolar molecules

Question 17

Which of the following best explains why sweating is an effective cooling mechanism for humans?

Accepted Answer

Evaporation of water requires energy, which is taken from the skin, lowering body temperature.

Question 18

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

Accepted Answer

$$	ext{Molarity} = \frac{	ext{moles of solute}}{	ext{liters of solution}}$$

Question 19

Which of the following best describes the relationship between $$\mathrm{CO}_2$$ and bicarbonate in aqueous solutions?

Accepted Answer

$$\mathrm{CO}_2$$ reacts with water to form carbonic acid, which dissociates into bicarbonate and hydrogen ions.

Water: Properties, Chemistry, and Biological Importance

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