Q: Which chemical equation represents the buffer system in human blood?

$CO_2 + H_2O \\rightleftharpoons H_2CO_3 \\rightleftharpoons HCO_3^- + H^+$

Question 1

If the concentration of hydrogen ions $[H^+]$ in a solution is $0.001$ moles/liter, what is the pH of the solution?

Accepted Answer

$pH = -\log_{10}(0.001) = 3$

Question 2

A patient arrives at the ER with a blood pH of $6.5$. What does this indicate about the hydrogen ion concentration compared to normal blood pH ($7.4$)?

Accepted Answer

Hydrogen ion concentration is higher than normal

Question 3

Which of the following best describes a buffer system in human blood?

Accepted Answer

A weak acid and its conjugate base that dissociate and re-associate reversibly

Question 4

If a solution’s pH changes from $5$ to $3$, by what factor has the hydrogen ion concentration changed?

Accepted Answer

It has increased by a factor of $100$

Question 5

Which chemical equation represents the buffer system in human blood?

Accepted Answer

$CO_2 + H_2O \rightleftharpoons H_2CO_3 \rightleftharpoons HCO_3^- + H^+$

Question 6

Aspirin (acetylsalicylic acid) is classified as a weak acid. What does this mean in terms of its behavior in water?

Accepted Answer

It partially dissociates, releasing some protons ($H^+$)

Question 7

During hyperventilation, what happens to the blood pH and why?

Accepted Answer

Blood pH increases because $CO_2$ is removed too quickly

Question 8

In the case study, Molly’s rapid breathing is a response to metabolic acidosis. What is the physiological purpose of this response?

Accepted Answer

To decrease $CO_2$ in the blood and raise pH

Question 9

If bicarbonate ($HCO_3^-$) is infused into a patient’s blood, which direction does the buffer equilibrium shift according to the Law of Mass Action?

Accepted Answer

Toward producing more carbonic acid ($H_2CO_3$)

Question 10

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

Accepted Answer

Weak bases are formed when weak acids partially dissociate

Question 11

A buffer is most effective when:

Accepted Answer

The weak acid and weak base are present in roughly equal and partially dissociated amounts

Question 12

If a patient’s blood pH drops from $7.4$ to $6.4$, what is the change in hydrogen ion concentration?

Accepted Answer

It increases by a factor of $10$

Question 13

Which of the following would NOT be a consequence of a blood pH below $7.0$?

Accepted Answer

Buffer systems become more effective

Question 14

What is the role of the bicarbonate ion ($HCO_3^-$) in the blood buffer system?

Accepted Answer

It acts as a proton acceptor

Question 15

Which of the following best explains why small changes in pH can have significant biological effects?

Accepted Answer

Because a change of 1 pH unit represents a ten-fold change in $[H^+]$

Question 16

If a person passes out from hyperventilating, what will happen to their blood pH as breathing returns to normal?

Accepted Answer

Blood pH will decrease back toward normal

Question 17

Which of the following is TRUE about the Law of Mass Action in the context of the blood buffer system?

Accepted Answer

Adding $CO_2$ shifts the equilibrium toward more $H_2CO_3$ and $H^+$

Question 18

Which of the following is a real-life consequence of metabolic acidosis caused by aspirin overdose?

Accepted Answer

Rapid and deep breathing to remove $CO_2$

Question 19

Which of the following equations correctly shows the dissociation of acetylsalicylic acid (aspirin) in water?

Accepted Answer

$acetylsalicylic\ acid \rightleftharpoons acetylsalicylate\ ion + H^+$

pH, Buffers, and Acid-Base Balance in Biology

Study Guide - Practice Questions

Study Guide - Flashcards