Question

In physical solvent systems, what specific relationship governs the amount of CO2 that dissolves into a liquid based on the partial pressure of the gas above it?

Accepted Answer

In physical solvent systems, the amount of CO2 that dissolves into a liquid is governed by Henry&#x27;s Law. This law states that the concentration of a dissolved gas in a liquid is directly proportional to the partial pressure of that gas above the liquid when the system is at equilibrium and at a constant temperature. The partial pressure is the portion of total gas pressure contributed by the CO2 specifically, representing its concentration in the gas phase. The mathematical relationship is expressed as C equals k times P, where C is the concentration of the dissolved gas, P is the partial pressure of the gas, and k is Henry&#x27;s Law constant, which is unique to the specific gas-liquid pair and temperature. Because physical absorption relies on these solubility forces rather than a chemical reaction, increasing the partial pressure of CO2 forces more gas molecules into the liquid phase, while decreasing the pressure allows the gas to escape. For example, in industrial gas processing using physical solvents like Selexol or Rectisol, the system operates by absorbing CO2 at high partial pressures and then releasing the CO2 by reducing the pressure or applying heat to lower the solubility, thus regenerating the solvent for reuse.

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In physical solvent systems, what specific relationship governs the amount of CO2 that dissolves into a liquid based on the partial pressure of the gas above it?