Question

multiple choice question
how do changes in co₂ concentration in seawater affect ph?
when co₂ increases, then ph decreases.
when co₂ decreases, then ph decreases.
when co₂ increases, then ph increases.

Explanation:

When carbon - dioxide ($CO_2$) dissolves in seawater, it forms carbonic acid ($H_2CO_3$). An increase in carbonic acid concentration leads to an increase in hydrogen - ion ($H^+$) concentration. Since pH is defined as $pH = -\log[H^+]$, an increase in $H^+$ concentration results in a decrease in pH.

Answer:

When $CO_2$ increases, then pH decreases.