Unformatted text preview: CHE4473 Kinetics Spring 2015 Homework N°2: Rate laws, reaction order, activation energy Due Tuesday JAN 20th 2015 ___________________________________________________________________________________________________ 1.
For a gas reaction at 400 K the rate is reported as: (a)
What are the units of the rate constant? (b) What is the value of the rate constant for this reaction if the rate equation is expressed as ___________________________________________________________________________________________________ 2. The pyrolysis of ethane proceeds with an activation energy of about 300 kJ/mol. How much faster is the decomposition at 650°C than at 500°C? Use R = 8.3144 J/mol K ___________________________________________________________________________________________________ 3. In the mid-‐nineteenth century the entomologist Henri Fabre noted that French ants (garden variety) busily bustled about their business on hot days but were rather sluggish on cool days. Checking his results with Oklahoma ants, we find Running speed, (meters/hr) Temperature, (°C) 150 13 160 16 230 22 295 24 370 28 What activation energy represents this variation in bustliness with temperature? ___________________________________________________________________________________________________ 4. The maximum allowable temperature for a reactor is 800 K. At present our operating set point is 780 K, the 20-‐K margin of safety to account for fluctuating feed, sluggish controls, etc. Now, with a more sophisticated control system we would be able to raise our set point to 792 K with the same margin of safety that we now have. By how much can the reaction rate, hence, production rate, be raised by this change if the reaction taking place in the reactor has an activation energy of 175 kJ/mol? ___________________________________________________________________________________________________ 5. A constant volume reaction AèP is being carried out a. If a 1000 liter CSTR is used with CA0 = 2 M and inlet flow rate of 10 L/min, what reaction rate (-‐rA) is required to achieve 70 % conversion? What is the concentration of A in the reactor? b. What rate would be required to achieve 95 % conversion in the CSTR? c. For the case of 70 % conversion of A, if the reaction is first order in A, what is the reaction rate coefficient k (include units)? And if the reaction is 2nd order in A? And if the reaction is ½ order in A? d. Using the value of the first-‐order coefficient k found in (c), if a 1000 L PFR were used instead of the CSTR, what would be the conversion? In your own words, explain why this conversion is greater than 70 % e. Using the value of the first-‐order coefficient k found in (c) if two CSTR’s in series (each with a volume of 500 L) were used instead of one of 1000 L, what would be the conversion? In your own words, explain why this conversion is greater than 70 % ...
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- Spring '14
- Reaction, 2 M, Fabre, 10 L