The equilibrium constants of gaseous chemical reactions are given in term of statistical thermodynamics, and calculated directly by the use of partition functions for both reactants and products.
Yeh, C. L. (2020). 具流線化轉角、阻氣環或向量壁之硫回收單元熱反應爐氮氧化物生成數值研究. 中國機械工程學刊, 41(4), 427-439. https://www.airitilibrary.com/Article/Detail?DocID=02579731-202008-202009230009-202009230009-427-439