Q: A solution has a hydroxide ion concentration $$[OH^-] of$$ $$1 \times 10$$^{-9}$$ M at 25°C. What is the hydrogen ion concentration $$[H^+]$$ in this solution?

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

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 without sinking?

Accepted Answer

Cohesion due to hydrogen bonding

Question 2

A scientist is studying a solution where the concentration of hydrogen ions $$[H^+] is$$ $$1 	imes 10$$^{-4}$$ M. What is the pH of this solution?

Accepted Answer

$$pH = 4$$

Question 3

Why does ice float on liquid water?

Accepted Answer

Hydrogen bonds in ice are more 'ordered,' making ice less dense than liquid water.

Question 4

Which of the following best explains why water is an effective temperature buffer for living organisms?

Accepted Answer

Water has a high specific heat due to hydrogen bonding, minimizing temperature fluctuations.

Question 5

A solution has a hydroxide ion concentration $$[OH^-] of$$ $$1 	imes 10$$^{-9}$$ M at 25°C. What is the hydrogen ion concentration $$[H^+]$$ in this solution?

Accepted Answer

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

Question 6

Which of the following scenarios best illustrates the concept of evaporative cooling?

Accepted Answer

Sweat evaporating from human skin, lowering body temperature.

Question 7

If the pH of a solution changes from 6 to 4, what happens to the hydrogen ion concentration?

Accepted Answer

It increases by 100 times.

Question 8

Which of the following best describes why water is called the 'universal solvent'?

Accepted Answer

Water's polarity allows it to dissolve many ionic and polar substances.

Question 9

A marine biologist observes that coral reefs are declining in areas with increased atmospheric $$CO_2. $$Which chemical process is most directly responsible for this decline?

Accepted Answer

Ocean acidification reduces carbonate ion concentration, hindering calcification.

Question 10

Which of the following statements about acids and bases is correct?

Accepted Answer

A strong acid dissociates completely in water, increasing $$[H^+].$$

Question 11

A buffer solution is added to a beaker of pure water. Which of the following best describes the function of the buffer?

Accepted Answer

It minimizes changes in $$[H^+]$$ and $$[OH^-]$$ when acids or bases are added.

Question 12

Which of the following best explains why oil does not mix with water?

Accepted Answer

Oil molecules are hydrophobic due to their nonpolar bonds.

Question 13

A researcher dissolves 18 g of glucose (molecular mass = 180 g/mol) in enough water to make 1 L of solution. What is the molarity of the solution?

Accepted Answer

$$0.1 M$$

Question 14

Which of the following is a consequence if ice were denser than liquid water?

Accepted Answer

All bodies of water would freeze solid from the bottom up, threatening aquatic life.

Question 15

Which of the following best describes the relationship between temperature and kinetic energy in water molecules?

Accepted Answer

Temperature measures the average kinetic energy of water molecules.

Question 16

A solution at 25°C has $$[H^+] = 1 	imes 10$$^{-8}$$ M. What is the $$[OH^-]$$ in this solution?

Accepted Answer

$$[OH^-] = 1 	imes 10$$^{-6}$$ M

Question 17

Which of the following best explains why water can dissolve salts such as sodium chloride ($$NaCl$$)?

Accepted Answer

Water's polarity allows it to surround and separate the ions, forming hydration shells.

Question 18

Which of the following is an example of adhesion?

Accepted Answer

Water molecules sticking to the walls of a plant cell.

Question 19

A student adds a strong acid to a buffered solution. What is the most likely outcome?

Accepted Answer

The buffer will minimize the change in pH.

Question 20

Which of the following best describes the process of ocean acidification?

Accepted Answer

Increased $$CO_2 in $$the atmosphere leads to more $$H^+ in $$seawater, lowering pH and reducing carbonate ion availability.

Water: The Molecule That Supports All of Life – Properties, Structure, and Biological Importance

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