Q: A lake has a measured pH of 4.0. What is the concentration of hydrogen ions $$[H^+] in $$the lake?

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

Question 1

Which property of water allows insects like water striders to walk on the surface of a pond without sinking?

Accepted Answer

High surface tension due to cohesion

Question 2

A water molecule is described as having a bent shape. What is the main reason for this molecular geometry?

Accepted Answer

The repulsion between lone pairs of electrons on the oxygen atom

Question 3

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

Accepted Answer

Hydrogen bonds in ice create a lattice that is less dense than liquid water

Question 4

A lake has a measured pH of 4.0. What is the concentration of hydrogen ions $$[H^+] in $$the lake?

Accepted Answer

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

Question 5

Which of the following is a direct result of water’s high specific heat for living organisms?

Accepted Answer

Stable internal and external environments

Question 6

If the pH of a solution changes from 6 to 8, how does the hydrogen ion concentration change?

Accepted Answer

It decreases by 100 times

Question 7

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

Accepted Answer

Buffers minimize changes in pH by accepting or donating $$H^+$$ ions

Question 8

A scientist adds NaCl to water. What happens at the molecular level?

Accepted Answer

Na$$^+$$ ions are attracted to the partial negative charge of oxygen atoms, and Cl$$^-$$ ions are attracted to the partial positive charge of hydrogen atoms

Question 9

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

Accepted Answer

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

Question 10

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

Accepted Answer

High heat of evaporation

Question 11

A protein requires a specific pH to function properly. What should be added to the solution to maintain this pH?

Accepted Answer

Buffer

Question 12

Which of the following best describes why water is an effective solvent for ionic compounds?

Accepted Answer

Water molecules form hydration shells around ions due to their polarity

Question 13

Which of the following substances would be considered hydrophobic?

Accepted Answer

Oil

Question 14

What is the pH of a solution with a hydrogen ion concentration of $$[H^+] = 10$$^{-9}$$ 	ext{ M}$$?

Accepted Answer

pH = 9

Question 15

Which of the following explains how water moves upward from roots to leaves in plants?

Accepted Answer

Cohesion and adhesion working together to counteract gravity

Question 16

If a solution has a pH of 7, which statement is true?

Accepted Answer

It is neutral and has equal concentrations of $$H^+$$ and $$OH^-$$

Question 17

Which of the following acts as a buffer in human blood?

Accepted Answer

Carbonic acid and bicarbonate ion

Question 18

A solution has a pH of 3. What is the hydroxide ion concentration $$[OH^-]$$?

Accepted Answer

$$[OH^-] = 10$$^{-11}$$ 	ext{ M}$$

Question 19

Which of the following is a consequence of water’s ability to absorb heat when hydrogen bonds break and release heat when they form?

Accepted Answer

Water stabilizes temperature in organisms and environments

Question 20

Which of the following best describes the difference between an acid and a base?

Accepted Answer

An acid increases $$H^+$$ concentration, a base decreases $$H^+$$ concentration

Water and Life: Structure, Properties, and Biological Importance

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