Question

exam lesson name: introduction to oceanography
exam number: 700793rr

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question 10 of 20 :
select the best answer for the question.

1. under acidic conditions, bicarbonate acts as a buffer in seawater by bonding to additional ______ ions, increasing the ph of the ocean.

○ a. carbonate
○ b. carbon dioxide
○ c. sulfate
○ d. hydrogen

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Explanation:

To solve this, we analyze the buffer action of bicarbonate ($\ce{HCO_3^-}$) in acidic conditions. In acidic seawater, there are excess $\ce{H^+}$ (hydrogen) ions. Bicarbonate acts as a buffer by reacting with $\ce{H^+}$ ions: $\ce{HCO_3^- + H^+
ightarrow H_2CO_3}$ (or related reactions that consume $\ce{H^+}$). This reduces the concentration of free $\ce{H^+}$ ions, thus increasing the pH. Let's evaluate the options:

• Option A: Carbonate ($\ce{CO_3^{2-}}$) would react with $\ce{H^+}$ too, but bicarbonate's buffer action in acid is about reacting with $\ce{H^+}$, not bonding to carbonate.
• Option B: Carbon dioxide ($\ce{CO_2}$) is not the ion bicarbonate bonds to for buffering in acid; instead, $\ce{H^+}$ is involved.
• Option C: Sulfate ($\ce{SO_4^{2-}}$) is unrelated to bicarbonate's buffer mechanism in seawater.
• Option D: Hydrogen ions ($\ce{H^+}$) are the ones bicarbonate bonds to (reacts with) to buffer acidic conditions, as this reaction consumes $\ce{H^+}$, raising pH.

Answer:

D. hydrogen