Q: A solution has a pH of 4. What is the concentration of hydrogen ions $$\left( [H^+] \right) in $$this solution?

$$[H^+] = 1 \times 10$$^{-4}$$ \ \mathrm{M}$$

Question 1

Which property of water allows it to moderate Earth's climate by absorbing and releasing large amounts of heat with only slight changes in its own temperature?

Accepted Answer

Its high specific heat capacity $$\left( c = \frac{q}{m \Delta T} \right)$$

Question 2

A scientist adds a drop of oil to a beaker of water. The oil forms a separate layer on top of the water. Which term best describes the oil's relationship to water?

Accepted Answer

Hydrophobic

Question 3

Why does ice float on liquid water, and what would be the consequence if it did not?

Accepted Answer

Ice is less dense than liquid water due to the formation of a crystalline lattice; if it did not float, most bodies of water would freeze solid, making life impossible.

Question 4

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 5

A solution has a pH of 4. What is the concentration of hydrogen ions $$\left( [H^+] \right) in $$this solution?

Accepted Answer

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

Question 6

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

Accepted Answer

Sweat evaporates from your skin, removing heat and cooling your body.

Question 7

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

Accepted Answer

An acid is a substance that increases the $$[H^+]$$ concentration of a solution.

Question 8

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

Accepted Answer

It minimizes changes in pH by combining reversibly with $$H^+$$ ions.

Question 9

Which of the following best describes the difference between cohesion and adhesion in water molecules?

Accepted Answer

Cohesion is the attraction between water molecules; adhesion is the attraction between water and other substances.

Question 10

A beaker contains a solution with a pH of 9. Which of the following statements is true about this solution?

Accepted Answer

It is basic and has a low $$[H^+]$$ concentration.

Question 11

Which of the following equations correctly represents the relationship between pH and hydrogen ion concentration?

Accepted Answer

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

Question 12

A student is studying the heat required to raise the temperature of 2 grams of water by 3 degrees Celsius. If the specific heat of water is $$1 \ \mathrm{cal} / (\mathrm{g} \cdot ^\circ \mathrm{C})$$, how much heat is required?

Accepted Answer

$$6 \ \mathrm{cal}$$

Question 13

Which of the following best explains why water has a high surface tension?

Accepted Answer

Hydrogen bonds between water molecules create a strong cohesive force at the surface.

Question 14

Which of the following is a real-life example of water's versatility as a solvent?

Accepted Answer

Salt dissolving in water to form seawater

Question 15

A solution contains a weak acid and its corresponding base. What is the primary function of this solution in a biological system?

Accepted Answer

To act as a buffer and minimize changes in pH

Question 16

Which of the following best describes the process that occurs when sodium chloride (NaCl) dissolves in water?

Accepted Answer

Na+ and Cl- ions are surrounded by hydration shells of water molecules due to water's polarity.

Question 17

Which of the following is NOT a property of water that facilitates life on Earth?

Accepted Answer

Low heat of vaporization

Question 18

If the concentration of $$[OH^-] in a $$solution is $$1 	imes 10$$^{-9}$$ \ \mathrm{M}$$, what is the pH of the solution?

Accepted Answer

pH = 5$$\ (	ext{since } [H^+] = 1 	imes 10$$^{-5}$$ \ \mathrm{M})$$

Question 19

Which of the following best explains why sweating is an effective way for humans to cool down?

Accepted Answer

Sweat absorbs heat from the body as it evaporates, due to water's high heat of vaporization.

Question 20

Which of the following best describes the role of hydrogen bonds in the unique properties of water?

Accepted Answer

They allow water molecules to stick together, resulting in cohesion, high specific heat, and surface tension.

Water and Its Biological Importance: Properties, Solutions, and Acid-Base Chemistry

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