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

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

Question 1

Which of the following best explains why water is considered a polar molecule?

Accepted Answer

Because the oxygen atom has a higher electronegativity, creating a partial negative charge near oxygen and a partial positive charge near hydrogen.

Question 2

Which type of bond is responsible for holding two water molecules together?

Accepted Answer

Hydrogen bond

Question 3

Which property of water allows insects, such as water striders, to walk on the surface of a pond?

Accepted Answer

Surface tension

Question 4

A scientist is studying how water helps regulate temperature in living organisms. Which property of water is most directly responsible for this effect?

Accepted Answer

High specific heat

Question 5

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

Accepted Answer

Ice is less dense than liquid water because its molecules form a crystalline lattice held by hydrogen bonds.

Question 6

Which of the following terms describes the attraction between water molecules and the walls of a plant's xylem vessels, helping water move upward against gravity?

Accepted Answer

Adhesion

Question 7

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

Accepted Answer

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

Question 8

Which of the following best explains why water is an excellent solvent for ionic and polar substances?

Accepted Answer

Water's polarity allows it to surround and separate ions and polar molecules.

Question 9

Which of the following equations correctly represents the dissociation of water?

Accepted Answer

$$H_2O \rightarrow H^+ + OH^-$$

Question 10

A beaker contains a solution with a high concentration of $$OH^-$$ ions. Which of the following best describes this solution?

Accepted Answer

It is basic and has a pH greater than 7.

Question 11

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

Accepted Answer

A buffer maintains a stable pH by accepting or donating $$H^+$$ ions.

Question 12

Which of the following is the correct definition of pH?

Accepted Answer

pH is the negative logarithm of the hydrogen ion concentration.

Question 13

If you add a strong acid to pure water, what happens to the pH and the $$[H^+]$$ concentration?

Accepted Answer

pH decreases and $$[H^+]$$ increases.

Question 14

Which of the following best describes the hydration shell in aqueous solutions?

Accepted Answer

A layer of water molecules that surrounds a solute ion, stabilizing it in solution.

Question 15

Which of the following is NOT a property of water that is important for life?

Accepted Answer

Low heat of vaporization

Question 16

A student mixes 0.1 M hydrochloric acid (a strong acid) with 0.1 M sodium hydroxide (a strong base). What is the expected pH of the resulting solution?

Accepted Answer

pH = 7

Question 17

Which of the following best explains why sweating helps cool the human body?

Accepted Answer

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

Question 18

Which of the following is the correct relationship between pH and $$[H^+]$$ concentration?

Accepted Answer

As pH increases, $$[H^+]$$ decreases.

Question 19

Which of the following best describes a hydrophobic substance?

Accepted Answer

A substance that does not interact with water and is repelled by it.

Question 20

Which of the following best explains why salt (NaCl) dissolves easily in water?

Accepted Answer

Water's polarity allows it to surround and separate Na+ and Cl- ions.

general biology unit 3

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