Q: Which equation correctly represents the relationship between hydrogen ion and hydroxide ion concentrations in pure water at 25°C?

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

Question 1

Which property of water is primarily responsible for the ability of some insects, such as water striders, to walk on the surface of a pond?

Accepted Answer

High surface tension due to cohesion

Question 2

Why does ice float on liquid water?

Accepted Answer

Hydrogen bonds in ice keep water molecules farther apart, making ice less dense

Question 3

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

Accepted Answer

Hydrogen bonds between water molecules absorb and release heat slowly

Question 4

A coastal city experiences milder temperatures than an inland city at the same latitude. Which property of water is most responsible for this phenomenon?

Accepted Answer

Water’s high specific heat moderates temperature

Question 5

Which equation correctly represents the relationship between hydrogen ion and hydroxide ion concentrations in pure water at 25°C?

Accepted Answer

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

Question 6

A solution has a pH of 4. What is the concentration of hydrogen ions in this solution?

Accepted Answer

$[H^+] = 10^{-4} 	ext{ M}$

Question 7

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

Accepted Answer

Buffers minimize changes in pH by reversibly binding H$^+$ ions

Question 8

Which property of water allows it to dissolve ionic compounds such as NaCl?

Accepted Answer

Water’s polarity and ability to form hydration shells around ions

Question 9

A scientist prepares 1 liter of a 1 M NaCl solution. What is the mass of NaCl required? (Na = 23 g/mol, Cl = 35.5 g/mol)

Accepted Answer

58.5 g

Question 10

Which of the following is a consequence of ocean acidification caused by increased atmospheric CO$_2$?

Accepted Answer

Decreased calcification in corals due to reduced carbonate ion concentration

Question 11

Which statement best explains why water is considered a polar molecule?

Accepted Answer

Oxygen attracts electrons more strongly, creating partial charges

Question 12

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

Accepted Answer

Olive oil

Question 13

If the pH of a solution changes from 7 to 5, how does the hydrogen ion concentration change?

Accepted Answer

It increases by 100 times

Question 14

Which process is responsible for cooling the skin when sweat evaporates?

Accepted Answer

Evaporative cooling due to heat absorption during vaporization

Question 15

A weak acid in a buffer solution helps maintain pH by:

Accepted Answer

Reversibly releasing and accepting H$^+$ ions

Question 16

Which of the following best describes the role of cohesion and adhesion in water transport in plants?

Accepted Answer

Cohesion holds water molecules together, and adhesion helps water stick to cell walls, counteracting gravity

Question 17

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

Accepted Answer

$	ext{pH} = -\log [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 viscosity

Question 19

A solution contains $1 	imes 10^{-8}$ M H$^+$ ions. What is its pH?

Accepted Answer

pH = 8

Question 20

Which real-world scenario best illustrates the importance of water’s high specific heat?

Accepted Answer

A lake remains relatively warm in autumn, supporting aquatic life even as air temperature drops

Chapter 3: Water and Life – Properties and Biological Importance of Water

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