NIST (National Institute of Standards and Technology, http://www.nist.gov/) has
ID: 948878 • Letter: N
Question
NIST (National Institute of Standards and Technology, http://www.nist.gov/) has compiled the experimentally measured solubility of CO2 in water into the following form: lnkH ?2600?1? 1 ? ,for 273K?T?303K 0?? kH ?T 298.15? with the Henry’s law constant at 298.15 K expressed as kH0 ? 0.034 mol/kg-bar where the “kg” unit is associated with the solvent and the “mol” and “bar” are associated with the solute. (a) Use kH0 to estimate the solubility of CO2, in terms of molar amount and mole fraction, in 1 kg of water in equilibrium with CO2 gas whose pressure is PCO2 = 1 bar. (b) Basedon (a), what are the component fugacity of the dissolved CO2 and fugacity of the pure liquid CO2 at 25 oC? (c) The air contains ~440 ppm of CO2. Estimate the equilibrium mole fraction of CO2 in water on a cold day at 0 oC.
2. NIST (National Institute of Standards and Technology, http://www.nist.gov/) has compiled the experimentally measured solubility of CO2 in water into the following form: In 2600 , for 273 KExplanation / Answer
2.(a): Applying Henry's equation,
solubility of CO2, Caq = KH0xP(CO2) = (0.034 mol / Kg.bar) x 1 bar = 0.034 mol / Kg (answer) or 0.034 mol / L (answer)
Now moles of CO2 in 1 Kg water = 0.034 mol CO2
moles of water in 1 Kg/9=1000 g) water = 1000 g / 18 g/mol = 55.55 mol
Hence moles fraction of CO2 = 0.034 mol / (55.55 mol + 0.034 mol) = 6.12x10-4 (answer)
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