What happens chemically when CO2 dissolves in seawater?

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Multiple Choice

What happens chemically when CO2 dissolves in seawater?

When CO2 dissolves in seawater, it forms carbonic acid, which then dissociates to hydrogen ions and bicarbonate. The extra H+ lowers the seawater’s pH and reacts with carbonate ions to make more bicarbonate. This shifts the carbonate system away from carbonate toward bicarbonate and dissolved CO2, so there are fewer CO3^2− ions available. That combination—more carbonic species and more acidity—drives the characteristic ocean acidification signal. So, the key point is that CO2 dissolving changes the chemical speciation in seawater, lowering pH and reducing carbonate availability. It doesn’t directly create more calcium carbonate; in fact, it makes building CaCO3 harder for marine organisms. The idea that there’s no chemical change isn’t accurate, and the notion of alkalinity increasing is not supported by this process, since added acidity tends to shift the system toward more bicarbonate and H+.

When CO2 dissolves in seawater, it forms carbonic acid, which then dissociates to hydrogen ions and bicarbonate. The extra H+ lowers the seawater’s pH and reacts with carbonate ions to make more bicarbonate. This shifts the carbonate system away from carbonate toward bicarbonate and dissolved CO2, so there are fewer CO3^2− ions available. That combination—more carbonic species and more acidity—drives the characteristic ocean acidification signal.

So, the key point is that CO2 dissolving changes the chemical speciation in seawater, lowering pH and reducing carbonate availability. It doesn’t directly create more calcium carbonate; in fact, it makes building CaCO3 harder for marine organisms. The idea that there’s no chemical change isn’t accurate, and the notion of alkalinity increasing is not supported by this process, since added acidity tends to shift the system toward more bicarbonate and H+.

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