ACS CP ACS CP Industrial & Process Chemistry 2 — Questions and Answers
Question 1: In chemical engineering, 'selectivity' in a reactor refers to:
- The ratio of actual yield to theoretical maximum yield of desired product
- The fraction of converted reactant that forms the desired product relative to all products (Correct answer)
- The efficiency of catalyst utilization expressed as turnover frequency
- The ratio of reaction rate to diffusion rate in a porous catalyst
Correct answer: The fraction of converted reactant that forms the desired product relative to all products
Selectivity is the fraction of converted starting material that yields the desired product versus all products formed, distinguishing it from yield (which also accounts for conversion).
Question 2: Process safety management (PSM) under OSHA 29 CFR 1910.119 applies to facilities that:
- Handle any amount of listed hazardous chemicals
- Handle highly hazardous chemicals above specified threshold quantities (Correct answer)
- Have more than 10 employees working with chemical processes
- Import or export regulated chemical substances
Correct answer: Handle highly hazardous chemicals above specified threshold quantities
OSHA PSM applies to processes involving highly hazardous chemicals at or above specified threshold quantities listed in Appendix A of 29 CFR 1910.119.
Question 3: Which type of reactor achieves uniform concentration and temperature throughout its volume at steady state?
- Plug flow reactor (PFR)
- Batch reactor
- Continuous stirred tank reactor (CSTR) (Correct answer)
- Fixed bed reactor
Correct answer: Continuous stirred tank reactor (CSTR)
The CSTR (also called a backmix reactor) operates with perfect mixing, resulting in uniform composition and temperature equal to the exit stream conditions throughout the vessel.
Question 4: In the chlor-alkali process, which products are co-produced at the anode and cathode respectively?
- Chlorine at anode; sodium hydroxide and hydrogen at cathode (Correct answer)
- Hydrogen at anode; chlorine and sodium at cathode
- Sodium at anode; chlorine and hydrogen at cathode
- Oxygen at anode; chlorine and NaOH at cathode
Correct answer: Chlorine at anode; sodium hydroxide and hydrogen at cathode
Electrolysis of brine (NaCl solution) produces Cl2 gas at the anode (oxidation of Cl⁻) and NaOH + H2 at the cathode (reduction of water).
Question 5: The Lower Explosive Limit (LEL) and Upper Explosive Limit (UEL) define:
- The minimum and maximum temperatures at which a vapor can ignite
- The concentration range of a flammable gas/vapor in air that can sustain combustion (Correct answer)
- The minimum and maximum pressures for safe operation of pressure vessels
- The lower and upper flash points of flammable liquids
Correct answer: The concentration range of a flammable gas/vapor in air that can sustain combustion
LEL and UEL define the flammable range — the concentration limits (% by volume in air) within which a fuel-air mixture can ignite and propagate a flame.
Question 6: Turnover frequency (TOF) in catalysis is defined as:
- Number of catalyst regeneration cycles per hour
- Number of substrate molecules converted per active site per unit time (Correct answer)
- Total mass of product formed per gram of catalyst per hour
- Ratio of active catalyst surface area to total surface area
Correct answer: Number of substrate molecules converted per active site per unit time
Turnover frequency (TOF) measures catalytic activity as the number of reactant molecules converted per catalytic active site per unit time (typically s⁻¹).
ACS CP ACS CP Industrial & Process Chemistry 2
In chemical engineering, 'selectivity' in a reactor refers to: