Question 1

Which property of water allows insects like water striders to walk on its surface without sinking?

Accepted Answer

Surface tension due to hydrogen bonding

Question 2

Why does ice float on liquid water, and why is this important for aquatic life in cold climates?

Accepted Answer

Ice is less dense than liquid water due to hydrogen bonding, allowing aquatic life to survive under the ice

Question 3

Which equation correctly defines pH?

Accepted Answer

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

Question 4

A solution has a hydrogen ion concentration of $$1 	imes 10$$^{-5}$$ M. What is its pH?

Accepted Answer

pH = 5

Question 5

Which of the following best describes a buffer?

Accepted Answer

A composition that resists changes in pH when small amounts of acids or bases are added

Question 6

Which equation is used to calculate the pH of a buffer solution containing a weak acid and its conjugate base?

Accepted Answer

$$\mathrm{pH} = \mathrm{p}K_a + \log_{10} \left( \frac{[\mathrm{A}^-]}{[\mathrm{HA}]} \right)$$

Question 7

If a buffer solution is made where $$[\mathrm{A}^-] = [\mathrm{HA}]$$, what is the relationship between pH and $$pK_a$$?

Accepted Answer

pH = $$pK_a$$

Question 8

Which of the following is a real-life example of the importance of buffers in the human body?

Accepted Answer

Buffers allow the body to maintain blood pH within a narrow range despite metabolic acid production

Question 9

Which of the following pairs is the main buffer system in human blood?

Accepted Answer

NaHCO$$_3 / H$_2CO$_3$$

Question 10

A patient is experiencing metabolic acidosis. Which organ is primarily responsible for compensating by excreting excess acid?

Accepted Answer

Kidney

Question 11

Which property of water is most responsible for its ability to dissolve ionic compounds like NaCl?

Accepted Answer

Polar nature and hydrogen bonding

Question 12

If the pH of a solution is 3, what is the concentration of hydrogen ions $$[\mathrm{H}^+]$$?

Accepted Answer

$$1 	imes 10$$^{-3}$$ M

Question 13

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

Accepted Answer

Hydrogen bonds between water molecules absorb heat energy

Question 14

Which of the following equations correctly relates pH and pOH in aqueous solutions at 25°C?

Accepted Answer

$$\mathrm{pH} + \mathrm{pOH} = 14$$

Question 15

A solution has a pOH of 5. What is its pH?

Accepted Answer

pH = 9

Question 16

Which of the following best describes the role of the bicarbonate buffer system in the human body?

Accepted Answer

It maintains blood pH by balancing H$$_2CO$_3$$ and HCO$$_3^-$$

Question 17

Which of the following is a correct statement about acids and bases according to the Brønsted-Lowry definition?

Accepted Answer

An acid is a proton donor and a base is a proton acceptor

Question 18

A buffer solution is prepared with 0.1 M acetic acid ($$\mathrm{p}K_a = 4.76) $$and 0.1 M sodium acetate. What is the pH of the solution?

Accepted Answer

pH = 4.76

Question 19

Which property of water is most important for the movement of water from roots to leaves in plants?

Accepted Answer

Cohesion and adhesion

Question 20

Which of the following best explains why antacids like Gelusil can relieve stomach acidity?

Accepted Answer

They act as buffers, neutralizing excess HCl in the stomach

Water, pH, and Buffers: Foundations of Biological Homeostasis

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