The utilization of natural gas reserves with high carbon dioxide (co2) content poses an enrichment problem that requires separation. in addition, the proposed use of co2 for enhanced oil recovery creates further need to characterize the vapor-liquid equilibrium properties of ch4-co2 mixtures. cryogenic distillation has been proposed at low temperatures (< -50 oc) and pressures below 4 mpa, where the formation of solid co2 is possible. investigate the vapor-liquid equilibrium behavior for the ch4-co2 mixture for mixtures containing 10, 30, 50, 80 mol% ch4. one source for experimental data for the ch4-co2 system is mraw, hwang, and kobayashi, journal of chemical engineering data, vol. 23 (2), p. 135 (1978). compare the phase equilibrium boundaries by using the peng robinson and soave-redlick-kwang equations of states and also adjusting the binary interactions parameter (kij) so that the model predictions match as closely as possible to existing experimental data.

Answerthis solution will not form a precipitateexplanationsolubility equilbrium:         pbf₂(s)  ⇄ pb²⁺(aq) + 2 f⁻(aq)the solubility product expression is    (we exclude solids from the equilibrium expression).now suppose we have the trial ion product q, which we can define as    then, we can interpret  q as the product of the concentration of the ions that we have and ksp as the product of the ion concentrations that are needed to form a saturated solution.if q > ksp, then that implies that there will be a surplus of ions that exceed the amount that is required to form a saturated solution. a precipitate will then form (the precipitate continually  forms until the surplus ions are removed and q is decreased to ksp's value).if q = ksp, the saturated solution that forms is barely saturated and the precipitate will be minimal.if q < ksp, then the ion concentration will not be enough to form a saturated solution (so no precipitate).using our information, we calculate the trial ion product:     since q = 2.7  × 10⁻⁸ < ksp =  4  ×  10⁻⁸, a precipitate will not form.

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