The equilibrium lies heavily toward NO2. Discussion: Brown 2 NO 2 (g) ⇌ N 2 O 4 (g) Colorless. Here is a graph of the pressures of NO2 and N2O4 as a function of time. [N2O4]=? NO 2 is extremely toxic and lethal even at concentrations as low as 200 ppm. At equilibrium, is the ratio [NO2]/[N2O4] less than, greater to, or equal to 1? What happens? In the gas phase, an equilibrium is established between NO2 and N2O4 molecules. Equilibrium is shifted to the N 2 O 4 side upon a decrease in temperature. Finding the Equilibrium Constant K For the equilibrium N2O4 2 NO2 Qc = [N O ] [NO ] 2 4 2 2 and K c = 0.491 at 100ºC Suppose we have 0.1000 moles N2O4 in a 0.1000 L flask, heated to 100ºC. ... so that their values in equilibrium constant expressions are always 1.00 that common ions precipitate all counter-ions Of these errors, up to ±3.5% was contributed by errors in the equilibrium constant,K p, in those measurements where the pressure was above 0.1 mbar. N The answer is C. The link below has a number of other examples of equilibrium constant calculations. The equilibrium constant of NO2 with N2O4 and the temperature dependence of the visible spectrum of NO2: A critical review and the implications for measurements of NO2 in the polar stratosphere Measurements of stratospheric NO2 by ground-based visible spectrometers rely on laboratory measurements of absorption cross-sections. [N2O4]init = 0.1000 mol / 0.1000 L = 1.000 M Result: 1.000 M N2O4 forms 0.588 M NO2. The ratio is equal to 1. The ratio is greater than 1. If the equilibrium mixture contains [NO2] = 0.047 M , what is the molar concentration of N2O4? Express the concentration to two significant figures and include the appropriate units. Chem. We review measurements and calculations ofK p, which were accurate to ±5% from 300 to 233 K. Each method was potentially flawed. The equilibrium constant is a dimensionless quantity. The equilibrium constant, Kc, for the reaction N2O4(g)⇌2NO2(g) is 4.6×10−3. At equilibrium, the expression for Keq is: Keq = [NO2]^2/[N2O4] = (1 x 10-2 mol/L)^2/(2 x 10-2 mol/L) = 5 x 10^-3. (oC) ∆G (kJ/mol N 2O4) K c 23 -5.13 8.03 70 3.14 0.334 100 8.41 0.0665 Data obtained from “The NBS Tables of Chemical Thermodynamic Properties,” J. Phys. Ref. Equilibrium Temp. The equilibrium constant is related to the free energy change for the reaction, G =o - RT lnK, (3) and Go, in turn, is related to the enthalpy and entropy changes, G o = H - T S. (4) We may evaluate Ho if we can measure K as a function of T, for we have R H (1/T) lnK o. The standard enthalpy (∆H rxn = -57.2 kJ) and the entropy (∆S rxn = -175.83 J) of reaction can be calculated from the following standard-state enthalpies of formation and standard-state entropies: Equilibrium is shifted to the N 2 O 4 side upon a decrease in temperature. Safety: Handle the tubes with extreme care. equilibrium. 2, 1982. The ratio is less than 1. Some N2O4 forms NO2.How much? 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