Directions

This simulation models the gas-phase reaction NO2 + CO → NO + CO2 in an isothermal plug flow reactor (PFR) and plots the concentration of each species versus reactor volume.

  • Use the Order of [NO2] and Order of [CO] sliders to change the exponents α and β in the rate law. When both orders equal the stoichiometric coefficients (1.0 and 1.0), the rate law corresponds to an elementary reaction.
  • Use the Inlet [NO2] and Inlet [CO] sliders to change the feed concentrations of the two reactants.
  • The rate expression and the units of the rate constant k update automatically above the sliders. Note how the units of k change as the total reaction order changes.
  • The slope of each curve is proportional to the local reaction rate; the curves flatten as reactants are consumed and the rate decreases.
  • Select Guided inquiry to download a worksheet with a structured activity that uses this simulation.

Details

The reaction rate is given by the power-law rate expression:

\( -r_{NO_2} = k \, C_{NO_2}^{\alpha} \, C_{CO}^{\beta} \)

For a plug flow reactor at steady state with constant volumetric flow rate, the mole balance on each species is:

\( \frac{dC_i}{dV} = \frac{r_i}{v_0} \)

From the stoichiometry of NO2 + CO → NO + CO2:

\( r_{NO_2} = r_{CO} = -k \, C_{NO_2}^{\alpha} \, C_{CO}^{\beta}, \qquad r_{NO} = r_{CO_2} = +k \, C_{NO_2}^{\alpha} \, C_{CO}^{\beta} \)

Because rate always has units of mol/(L s), the units of the rate constant depend on the total order \( n = \alpha + \beta \):

\( [k] = \left( \mathrm{mol/L} \right)^{1-n} \, \mathrm{s}^{-1} \)

Symbols:

  • \( C_i \) = concentration of species \( i \) (mol/L)
  • \( V \) = reactor volume (L)
  • \( v_0 \) = volumetric flow rate = 5.0 L/s
  • \( k \) = rate constant = 0.5 (units depend on total order)
  • \( \alpha, \beta \) = reaction orders with respect to NO2 and CO
  • \( n = \alpha + \beta \) = total reaction order

The mole balances are integrated numerically (Euler method, 200 steps) from \( V = 0 \) to \( V = 50 \) L.

About

This simulation was generated by Professor David L. Silverstein and Dr. Loyal Murphy of the University of Mississippi using Google Gemini. It was modified for LearnChemE using Claude AI.

-rNO2 = k [NO2]1.0 [CO]1.0
k = 0.5 L·mol⁻¹·s⁻¹; flow rate = 5.0 L/s