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.303Easy
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.304Medium
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.305Medium
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)
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Q.306Easy
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.307Easy
In an isothermal CSTR, if feed concentration C_A0 = 10 mol/m³ and outlet concentration C_A = 2 mol/m³, conversion is:
In enzyme catalysis, what does the Michaelis-Menten constant (K_m) represent?
Answer: A
K_m represents substrate concentration [S] at which reaction velocity = V_max/2
Q.312Medium
For an exothermic reaction in an adiabatic reactor, what happens to the reaction rate as conversion increases?
Answer: C
Adiabatic reactor: no heat removal; exothermic reaction raises temperature, increasing k and hence rate
Q.313Hard
Which approximation is used in steady-state kinetics for enzyme reactions?
Answer: D
Both steady-state (d[ES]/dt = 0) and pre-equilibrium approximations are used in Michaelis-Menten derivation
Q.314Medium
For autocatalytic reactions, which reactor gives highest conversion at equilibrium?
Answer: D
Equilibrium conversion is thermodynamically determined and independent of reactor type
Q.315Easy
In a fluidized bed reactor (FBR), particles exhibit properties of both solids and fluids. What is this phenomenon called?
Answer: B
Fluidization: particles suspended in gas/liquid flow with properties intermediate between fixed bed and fluid
Q.316Hard
For consecutive reactions A→B→C, the concentration of intermediate B is maximum at time t_max. This time depends on:
Answer: A
t_max = ln(k₂/k₁)/(k₂-k₁), depends only on rate constants, independent of [A]₀
Q.317Easy
In a batch reactor operating at constant volume, the rate of reaction for a first-order reaction A→B is -rA = kCA. If the initial concentration is 2 mol/L and k = 0.1 min⁻¹, what will be the concentration after 10 minutes?
What is the primary advantage of a plug flow reactor (PFR) over a continuous stirred-tank reactor (CSTR) for reactions with high activation energy?
Answer: C
PFR provides higher conversion than CSTR for the same volume because of better concentration gradient utilization and no back-mixing of unreacted material
Q.319Easy
In the context of reaction kinetics, which statement best describes the rate-determining step (RDS) in a multi-step reaction mechanism?
Answer: B
The rate-determining step is the slowest elementary step in the reaction mechanism, which governs the overall rate of the reaction regardless of its position in the sequence
Q.320Medium
For a second-order reaction A+B→C with equal initial concentrations of 1 mol/L, if the rate constant is 0.5 L/(mol·min), what is the time required for 50% conversion?
Answer: A
For second-order reaction with CA0 = CB0: 1/CA - 1/CA0 = kt. At 50% conversion, CA = 0.5. So (01.5 - 11) = 0.5×t gives t = 2 minutes