All Free Chemical Engineering MCQs with Answers
Every Chemical Engineering question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
6,983 questions · page 180 of 350
- A. Equilibrium constant
- B. Heat of reaction
- C. Heat of formation of the product
- D. Activation energy
Explanation: A catalyst provides an alternative reaction pathway with a lower activation energy, thereby increasing the rate in both directions.
Correct answer: Activation energy- A. η = θ, for an isothermic tubular reactor in which the density of the process fluid is constant
- B. η = θ, when the fluid density changes in the reactor
- C. η and θ are always equal
- D. η = θ, for a non-isothermal reactor
Explanation: Space time equals residence time when the fluid density, and hence volumetric flow rate, remains constant through the reactor.
Correct answer: η = θ, for an isothermic tubular reactor in which the density of the process fluid is constant- A. Batch
- B. Mixed
- C. Plug-flow
- D. None of these
Explanation: A mixed-flow reactor gives uniform concentration and temperature throughout the reacting mixture, making the rate easier to evaluate for a…
Correct answer: Mixed- A. 1/(time)(concentration)n - 1
- B. (Time)-1 (concentration)n - 1
- C. (Time)n - 1 (concentration)
- D. None of these
Explanation: For -r = kC^n, the rate constant has units of concentration^(1-n) per time, equivalent to 1 divided by time times concentration^(n-1).
Correct answer: 1/(time)(concentration)n - 1- A. Porosity of the catalyst bed
- B. Pore size distribution
- C. Pore diameter
- D. Specific surface of a porous catalyst
Explanation: BET adsorption analysis measures the specific surface area by determining the amount of gas required to form a monolayer on the solid.
Correct answer: Specific surface of a porous catalyst- A. Pore diffusion
- B. Gas film
- C. Chemical reaction
- D. None of these
Explanation: The effectiveness factor compares the actual pellet reaction rate with the rate if internal diffusion caused no limitation, so it…
Correct answer: Pore diffusion- A. (i) endothermic (ii) exothermic
- B. (i) exothermic (ii) exothermic
- C. (i) endothermic (ii) endothermic
- D. (i) exothermic (ii) endothermic
Explanation: Catalytic cracking consumes heat, so it is endothermic, while burning the deposited coke during catalyst regeneration releases heat and is…
Correct answer: (i) endothermic (ii) exothermic- A. High capacity
- B. Presence of lateral mixing
- C. Presence of axial mixing
- D. Constant composition and temperature of reaction mixture
Explanation: An ideal plug-flow reactor has no axial mixing, but fluid elements can mix laterally or radially.
Correct answer: Presence of lateral mixing- A. 4
- B. 16
- C. 8
- D. 2
Explanation: With the same reactant amounts and temperature, reducing the volume to one-fourth makes both concentrations four times larger.
Correct answer: 16- A. Neither A. nor B.
- B. Concentration
- C. Both A. & B.
- D. Reaction rate
Explanation: At steady state, an ideal CSTR is perfectly mixed and its concentration and reaction rate remain constant with time.
Correct answer: Neither A. nor B.3591. The enzyme which can catalyse the conversion of glucose to ethyl alcohol is ___________________?
- A. Invertase
- B. Zymase
- C. Diastase
- D. Maltase
Explanation: Zymase is the enzyme complex in yeast that converts glucose into ethanol and carbon dioxide during alcoholic fermentation.
Correct answer: Zymase- A. Initial concentration of reactants
- B. Time of reaction
- C. Temperature of the system
- D. Extent of reaction
Explanation: The rate constant is primarily determined by temperature through the Arrhenius relation k = A exp(-Ea/RT).
Correct answer: Temperature of the system- A. 0
- B. 1
- C. 1.5
- D. 2
Explanation: In a batch reactor, a linear increase of conversion with time means dX/dt is constant.
Correct answer: 0- A. Constant fluid density systems
- B. Variable fluid density systems
- C. Non-isothermal gas reaction
- D. Gas reactions with changing number of moles
Explanation: Space time is V divided by the inlet volumetric flow rate, whereas holding time uses the actual flow rate inside the reactor.
Correct answer: Constant fluid density systems3595. For a zero order reaction, the concentration of product increases with the _____________________?
- A. Total pressure
- B. Increase in initial concentration
- C. Increase of reaction time
- D. Decrease in total pressure
Explanation: For a zero-order reaction, the product formation rate is constant, so product concentration increases linearly with reaction time.
Correct answer: Increase of reaction time- A. 2/3
- B. 3/8
- C. 1/3
- D. 5/8
Explanation: For 2A ⇌ B, the total moles decrease as A reacts, giving ε = −0.8/2 = −0.4. At X = 0.5, CA/CA0 = (1 − X)/(1 + εX) = 0.5/0.8 = 5/8.
Correct answer: 5/8- A. Temperature should be high in the beginning and decreased towards the end of the reaction
- B. Very low temperature should be used throughout the reaction
- C. Very high temperature should be used throughout the reaction
- D. None of these
Explanation: For an exothermic reversible reaction, high temperature is useful near the inlet for rapid reaction, but temperature should fall toward…
Correct answer: Temperature should be high in the beginning and decreased towards the end of the reaction- A. Zero
- B. First
- C. Second
- D. Third
Explanation: If the rate depends on only one concentration raised to the first power, the reaction is first order.
Correct answer: First3599. When a catalyst increases the rate of chemical reaction, the rate constant_____________________?
- A. Decreases
- B. Remain constant
- C. Increases
- D. Become infinite
Explanation: A catalyst provides an alternative pathway with lower activation energy, so at the same temperature its effective rate constant is higher.
Correct answer: Increases- A. Lose a proton
- B. None of these
- C. Gain an electron
- D. Gain a proton
Explanation: A Brønsted base accepts a proton, so base catalysis is associated with substances having a tendency to gain H+.
Correct answer: Gain a proton