Chemical Engineering questions for GATE and PSU exams are built on a handful of core subjects applied in many ways. Practice spans fluid mechanics, heat transfer, mass transfer, chemical reaction engineering, thermodynamics, process control and instrumentation, and plant design economics. Numerical solutions carry the assumptions written out, because the assumption is usually what separates a correct answer from a plausible one.
Which type of reactor provides the best conversion for a reversible exothermic reaction?
Answer: C
PFR with heat removal maintains optimal temperature profile and continuous removal of products, favoring forward reaction equilibrium
Q.3Easy
For a zero-order reaction, the integrated rate law is:
Answer: A
Zero-order integrated rate law: [A] = [A]₀ - kt, linear with time
Q.4Medium
In a CSTR operating at steady state, if residence time is doubled and inlet concentration remains constant, how does conversion change for a first-order reaction?
Answer: B
For CSTR: X = kτ/(1+kτ). Increasing τ increases conversion for first-order reactions
Q.5Hard
What is the activation energy for a reaction if its rate constant doubles when temperature increases from 300K to 310K?
For parallel reactions A→B and A→C, the selectivity of B over C is defined as:
Answer: A
Selectivity = rate of desired product formation/rate of undesired product formation
Q.7Easy
Which statement is correct about the residence time distribution (RTD) in an ideal plug flow reactor?
Answer: B
In ideal PFR, E(t) = δ(t-τ), meaning all molecules have identical residence time equal to τ
Q.8Medium
In a catalytic reaction, which parameter does NOT affect the rate of reaction?
Answer: C
Catalyst doesn't change ΔG or equilibrium position; it only lowers Eₐ. ΔG determines feasibility, not rate
Q.9Medium
For the reaction 2A → B, if initial concentration of A is 2 mol/L and concentration after 5 minutes is 1 mol/L, calculate rate constant (assuming second-order):
Answer: A
For 2nd order: 1/[A] = 1/[A]₀ + kt; 11 = 21 + k(5); k = 0.1 L/(mol·min)
Q.10Easy
What is the order of reaction if the rate law is: rate = k[A]^(21)[B]?
Answer: B
Order = sum of exponents = 21 + 1 = 1.5 (fractional order, common in enzyme kinetics)
Q.11Easy
In an isothermal CSTR, if feed concentration C_A0 = 10 mol/m³ and outlet concentration C_A = 2 mol/m³, conversion is:
