lecture 8

Question 1

What is the pH range of seawater, and what does this indicate?

Answer 1

Seawater pH is between 8.0 and 8.3, averaging around 8.1 at the surface. This alkaline (basic) range indicates that seawater is buffered, maintaining a relatively constant pH by balancing the concentration of hydrogen ions.

Question 2

How does carbon dioxide (CO2) interact with seawater?

Answer 2

Carbon dioxide dissolves in seawater, forming carbonic acid (H2CO3) which dissociates into bicarbonate (HCO3-) and carbonate (CO3-2) ions, releasing hydrogen ions (H+). These reactions are reversible, helping to buffer the pH of seawater.

Question 3

What role does buffering play in seawater pH?

Answer 3

Buffering involves reactions that can add or remove hydrogen ions (H+) to maintain the seawater pH within a narrow range. This system primarily involves carbon dioxide, carbonic acid, bicarbonate, and carbonate reactions.

Question 4

What is the significance of dissolved gases in seawater?

Answer 4

Dissolved gases like carbon dioxide (CO2), oxygen (O2), and nitrogen (N2) are crucial for marine life. The interaction between CO2 and seawater plays a significant role in controlling the ocean’s pH and affects marine ecosystems.