How does the amount of \(\mathrm{CO}_2\) in the atmosphere correlate with the amount of \(\mathrm{CO}_2\) in the water \(\left(\mathrm{pCO}_2\right)\) ? How does the \(\mathrm{pH}\) of seawater correlate with the amount of \(\mathrm{CO}_2\) in the water?

CO2 from the atmosphere dissolves in seawater, forming carbonic acid (H2CO3). As the concentration of CO2 in the atmosphere increases, the concentration of dissolved CO2 in seawater also increases. This direct relationship between atmospheric CO2 and pCO2 in seawater is known as Henry's Law, which states that the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid. Mathematically, this can be represented as: \( pCO_2 = K_H \times [CO_2] \) where \(pCO_2\) is the partial pressure of CO2 in seawater, \(K_H\) is Henry's Law constant, and \([CO_2]\) represents the concentration of CO2 in the atmosphere. As the atmospheric CO2 concentration increases, the pCO2 in seawater also increases, as described by Henry's Law.

When CO2 dissolves in seawater, it forms carbonic acid (H2CO3), which can dissociate into bicarbonate (HCO3-) and hydrogen ions (H+), and further dissociate into carbonate (CO32-) and more hydrogen ions: \( CO_2 + H_2O \rightleftharpoons H_2CO_3 \rightarrow HCO_3^- + H^+ \rightarrow CO_3^{2-} + 2H^+ \) The increase of hydrogen ions (H+) in the water due to this process lowers the pH of the seawater. pH is defined as the negative log of the hydrogen ion concentration: \( pH = -\log_{10}[H^+] \) As the pCO2 in the water increases, the hydrogen ion concentration also increases, and the pH of seawater decreases. This indicates an inverse relationship between the pH of seawater and the amount of CO2 in the water. In conclusion: - The amount of CO2 in the atmosphere and the pCO2 in seawater are directly related according to Henry's Law. As the atmospheric CO2 concentration increases, the pCO2 in seawater also increases. - The pH of seawater is inversely related to the amount of CO2 in the water. As the concentration of dissolved CO2 increases, the hydrogen ion concentration increases, and the pH of seawater decreases.