Question

1. Scientific studies show that the shelled organisms in the ocean begin to dissolve at lower pH. What are shells composed of? Explain why the shells are more soluble at lower pH? Use chemical reactions to support your answer.

Answer 1

The carbon dioxide present in the atmosphere dissolves in the sea water, the water molecules combine with carbon dioxide molecules to form carbonic acid. As a result of this, the acidity of the sea water increases. thus pH value is low. therefore, the concentration of H⁺ ions is high.

The shells are mostly composed of calcium carbonate CaCO₃. The H⁺ ions also have tendency to combine with carbonate ion. The H⁺ ions have greater attraction to combine with the carbonate ion than the calcium ion to form bicarbonate ion (HCO₃^-). As a result the shells get dissolved forming bicarbonate ions at high concentration of hydronium ion.