According to \"Chlor-alkali Technology\", the temperature of hydrogen and chlorine in the electrolyzer is the same, but the amount of water discharged differs by a factor of three
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This post was last edited by sunjl1981 on 2013-1-6 23:42. Experts on this forum, how should this issue be understood? Using p1: P2=n1:n2, the amount of water vapor carried away on the chlorine-hydrogen sides should be similar; moreover, both chlorine and hydrogen are non-polar molecules. Using Raoult’s law, the molar fraction of saltwater leaving the system is 6.13%, while the molar fraction of alkali leaving is 17.68%. According to Raoult’s law, the difference in water vapor carried away should be around 20%. However, hydrogen carries away an amount of water vapor equal to x, whereas chlorine carries away 3x. How can this be explained? Is it determined through experimental measurements? Is it still because sodium chloride and sodium hydroxide have different attractions for water vapor, which is why the amount of water vapor they remove differs so much? # + + .
Raoult’s law applies to ideal solutions, or to dilute solutions of non-electrolytes. And saline and caustic soda solutions are strongly polar electrolyte solutions at equilibrium; are they not applicable? Should we use a liquid-phase activity coefficient model and a gas-phase ideal gas model to determine this equilibrium? I hope to discuss this with everyone
The original poster seems to have misunderstood Raoult’s law. Raoult’s law relates to the vapor pressure of the solvent, whereas the poster is comparing the solute; the solute, at the temperature of the tank, is an inert substance (a strong electrolyte) and therefore does not form a mixed vapor. Applying Raoult’s law to calculate the moisture content in hydrogen and chlorine also works, and the differences should be minimal
This is because the vapor pressures of water vapor on the anode and cathode sides are different; the anode side has an 18% NaCl solution (200 g/l), while the cathode side has a 32% sodium hydroxide solution. At 90 degrees, the vapor pressure of water vapor at the anode is 438.2 mmHg, and that at the cathode is 270 mmHg (data sourced from sources such as Chlor-Alkali Technology). According to the law of partial pressures for mixed gases, the molar ratio is equal to the pressure ratio. . This allows us to calculate the amount of water taken away from each side. .