Suppose that the exhaust stream of an automobile has a flow rate of 2.55 L/s at 655 K and contains a partial pressure of NO of 12.4 torr. What total mass of urea is necessary to react completely with the NO formed during 8.0 hours of driving?

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1. Convert the flow rate from liters per second (L/s) to liters per hour (L/h) by multiplying by the number of seconds in an hour.
2. Calculate the total volume of the exhaust stream over 8.0 hours using the flow rate in L/h.
3. Use the ideal gas law, PV = nRT, to find the number of moles of NO in the exhaust stream. Remember to convert the pressure from torr to atm and use the appropriate value for R (0.0821 L·atm/mol·K).
4. Determine the stoichiometry of the reaction between urea and NO. The balanced chemical equation is: 2 NO + (NH2)2CO → N2 + CO2 + 2 H2O.
5. Calculate the mass of urea needed using the stoichiometry from the balanced equation and the molar mass of urea (60.06 g/mol).