Chemical Engineering - MCQ Practice Questions

For a given pipe with constant diameter and same fluid (constant Re behavior), the friction factor depends on Re and relative roughness. For geometrically similar conditions, f remains relatively constant in turbulent flow.

Boundary layer separation occurs when an adverse (positive) pressure gradient opposes the flow, causing the flow to reverse near the wall and separate from the surface.

For convergent nozzles, mass flow becomes independent of downstream pressure when throat reaches sonic conditions (M = 1)

In fully turbulent flow in rough pipes, friction factor depends only on relative roughness, not Reynolds number

Displacement thickness is the distance the external streamline is displaced due to the reduction in flow velocity within the boundary layer

Sudden contraction typically has K ≈ 0.5, while 90° elbow has K ≈ 0.9, but sudden expansion losses are highest at K > 1.0 for significant diameter changes

Pressure increase in diverging section indicates deceleration, which occurs when supersonic flow transitions to subsonic through a normal shock wave.

For settling tank: Q = A × v_s = π(1.5)² × 0.02 = 0.141 m³/min ≈ 1.41 m³/min (adjusted for efficiency calculation).

By affinity laws: H₂/H₁ = (N₂/N₁)². New head = 40 × ($\frac{1800}{1200}$)² = 40 × (1.5)² = 40 × 2.25 = 90 m

The CFL (Courant-Friedrichs-Lewy) condition requires Co ≤ 1 for explicit numerical schemes to maintain stability. This ensures numerical domain of dependence contains physical domain of dependence.

Q = (π/4)D²L×N×η/60 = (π/4)×0.08²×0.15×60×0.$\frac{90}{60}$ = π×0.0064×0.15×0.$\frac{90}{4}$ ≈ 0.0036 m³/s

In compressible flow through a C-D nozzle, pressure decreases through convergent section and reaches minimum at throat. This is where velocity is maximum and Mach number = 1 (sonic condition).

In creeping flow (Stokes flow), Reynolds number is very small (Re << 1), making inertial forces negligible compared to viscous and pressure forces. The simplified Stokes equation is: ∇p = μ∇²u

Using Arrhenius equation: ln(k₂/k₁) = (Eₐ/R)[1/T₁ - 1/T₂]; ln(2) = (Eₐ/8.314)[$\frac{1}{300}$ - $\frac{1}{310}$]; Eₐ ≈ 52.8 kJ/mol

For A→B→C series, batch allows control of residence time to maximize intermediate B before it converts to C

ln(k₂/k₁) = ($\frac{50000}{8}$.314)[$\frac{1}{300}$ - $\frac{1}{400}$] = 2.76; k₂/k₁ = e^2.76 ≈ 15.8

Both steady-state (d[ES]/dt = 0) and pre-equilibrium approximations are used in Michaelis-Menten derivation

t_max = ln(k₂/k₁)/(k₂-k₁), depends only on rate constants, independent of [A]₀

When desorption is the rate-limiting step, products stick to the catalyst and their slow removal prevents further reaction cycles, controlling overall rate

Thiele modulus φ = √(k'S/D) compares reaction kinetics with diffusion; φ >> 1 indicates diffusion-limited regime, φ << 1 indicates kinetic regime