In a mixed flow reactor carrying out the reaction A → 3R, the conversion is 50% when gaseous reactant ‘A’ enters at 1 litre/second and leaves at 2 litres/second. The holding time for this process is _______________ seconds?
Show answer Hide answer
Answer: A. 0.5
Explanation
Holding time in a mixed flow reactor equals the reactor volume divided by the exit volumetric flow rate for variable density systems. Stoichiometric expansion for the reaction A to 3R doubles the volumetric flow rate from inlet to outlet. Dividing the system parameters correctly yields a holding time value of 0.5 seconds. Holding time represents the average duration fluid elements remain inside a continuous stirred tank reactor. Gas-phase reactions involving changes in total moles experience significant volumetric expansion during conversion. Mixed flow reactors assume complete and instantaneous blending of fluid contents throughout the vessel.
Calculating holding times correctly ensures that continuous reactors possess sufficient volume for complete reactions. Volumetric expansion must be accounted for in gas phase reactor design to avoid underestimating required sizes. Chemical engineers rely on accurate residence time metrics when designing safe high-pressure gas reactors. Option B suggesting 1 second ignores the doubling of volumetric flow rate caused by gas stoichiometry. Option C proposing 2 seconds miscalculates the volumetric expansion ratio of the reacting gas mixture. Option D predicting 3 seconds fails to apply proper reactor sizing and flow rate equations.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
Related questions
Q1. For a reactant undergoing a first-order reaction, what is the conversion level at a time equal to three times the reaction half-life?
Show answer Hide answer
Answer: A. 0.875
The fraction of reactant remaining after n half-lives in a first-order reaction equals one over two to the power of n. After three half-lives, the fraction remaining is one-eighth, which equals 0.125 of the initial conce...
Q2. Space velocity is defined as____________________?
Show answer Hide answer
Answer: D. All A., B. and C.
Space velocity characterizes tubular reactor performance, maximum feed capacity, and reaction ease. High space velocity values indicate short residence times and large processing capacities per unit reactor volume. React...
Q3. When collecting conversion XA and residence time data for a zero-order liquid-phase reaction in a stirred tank reactor, which plot will yield a straight line?
Show answer Hide answer
Answer: A. XA Vs . η
For a zero-order liquid-phase reaction in a continuous stirred tank reactor, conversion equals the rate constant multiplied by space time divided by initial concentration. Because conversion is directly proportional to s...
Q4. The transient energy balance equation for a tubular reactor is expressed as________________?
Show answer Hide answer
Answer: C. A linear partial differential equation
The transient energy balance for a tubular reactor results in a linear partial differential equation.
Q5. The ‘E’ function for a non-ideal reactor represents the fraction of fluid with ages between t and t + dt_____________________?
Show answer Hide answer
Answer: B. At the outlet
The exit age distribution function E characterizes the residence time distribution of fluid leaving a reactor. It represents the exact fraction of the effluent stream whose internal ages fall between t and t plus dt. Mea...
Q6. The activation energy of a chemical reaction ?
Show answer Hide answer
Answer: B. Is the minimum energy which the molecules must have before the reaction can take place
Activation energy is defined as the minimum energy that reacting molecules must possess for a chemical reaction to occur. Reactants must overcome this energetic threshold before old chemical bonds can break and new bonds...