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SCE–Qiyas Engineering Fundamentals – Chemical: free practice test

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Practice test questions with answers and explanations

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01Acetic acid (Ka = 1.8×10⁻⁵) has a concentration of 0.10 M. What is the pH?

Practice question Unit: Chemistry Foundation

  1. A4.74

    4.74 is approximately pKa, not the solution pH.

  2. B1.00

    pH 1 assumes complete dissociation of 0.10 M acid.

  3. C3.38

    3.38 is inconsistent with [H⁺] ≈ √(KaC).

  4. D2.88 ✓ Correct answer

    [H⁺] ≈ √(1.8×10⁻⁵×0.10) = 1.34×10⁻³ M; pH ≈ 2.88.

Reference: SCE–Qiyas Engineering Fundamentals – Chemical, Chemistry Foundation – CHE-T1-01..08 Acids/bases, concentration, equilibrium, gas laws

021000 kg/h of a 40 wt% benzene feed is split into a distillate of 95 wt% and bottoms of 5 wt% benzene. What is the distillate rate?

Practice question Unit: Chemical Engineering Principles

  1. A389 kg/h ✓ Correct answer

    D = 1000(0.40−0.05)/(0.95−0.05) = 388.89 kg/h.

  2. B421 kg/h

    421 kg/h does not satisfy both component and total balances.

  3. C611 kg/h

    611 kg/h is approximately the bottoms flow, not the distillate.

  4. D400 kg/h

    400 kg/h is the benzene feed, not the distillate stream.

Reference: SCE–Qiyas Engineering Fundamentals – Chemical, Chemical Engineering Principles – CHE-T2-01..06 Units, process variables and material balances

031 mol of ideal gas expands reversibly and isothermally at 300 K from 1 L to 5 L. What is the work done by the gas? Use R = 8.314 J/(mol·K).

Practice question Unit: Chemical Engineering Thermodynamics

  1. A499 J

    499 J is too small for nRT ln(5).

  2. B9,977 J

    9977 J incorrectly scales work with the volume difference.

  3. C1,743 J

    1743 J uses log10 rather than the natural logarithm.

  4. D4,014 J ✓ Correct answer

    W = nRT ln(V₂/V₁) = 8.314×300×ln5 ≈ 4014 J.

Reference: SCE–Qiyas Engineering Fundamentals – Chemical, Chemical Engineering Thermodynamics – CHE-T3-01..06 First/second law, EOS, entropy, lost work

04Water flows steadily at 1.0 m/s through a 10 cm diameter pipe into a 5 cm diameter pipe. Assuming incompressible flow, what is the velocity in the smaller pipe?

Practice question Unit: Fluid Mechanics

  1. A4.00 m/s ✓ Correct answer

    v₂ = v₁(D₁/D₂)² = 1×(10/5)² = 4.00 m/s.

  2. B0.250 m/s

    0.250 reverses the required area ratio.

  3. C8.00 m/s

    8.00 uses the diameter ratio cubed rather than squared.

  4. D2.00 m/s

    2.00 uses a diameter ratio instead of an area ratio.

Reference: SCE–Qiyas Engineering Fundamentals – Chemical, Fluid Mechanics – CHE-T4-01..07 Statics, energy balance, friction and fittings

05What is the net radiation from a 1.0 m² gray surface (ε = 0.90) at 500 K to large surroundings at 300 K? Use σ = 5.67×10⁻⁸ W/(m²·K⁴).

Practice question Unit: Heat Transfer

  1. A3,084 W

    3084 W omits the surface emissivity of 0.90.

  2. B81.6 W

    81.6 W does not apply the fourth-power radiation relation.

  3. C2,776 W ✓ Correct answer

    q = εσA(500⁴−300⁴) ≈ 2776 W.

  4. D3,189 W

    3189 W ignores radiation received from the surroundings.

Reference: SCE–Qiyas Engineering Fundamentals – Chemical, Heat Transfer – CHE-T5-01..05 Modes of heat transfer and coefficients

06Gas-liquid equilibrium y = 0.50x (y, x mole fractions). Gas at the interface has y = 0.050. Interface liquid x?

Practice question Unit: Mass Transfer

  1. A0.0500

    0.050 is y; liquid x is twice y.

  2. B0.100 ✓ Correct answer

    x = y/0.50 = 0.050/0.50 = 0.100.

  3. C0.0250

    0.025 multiplies y by 0.50 instead of dividing.

  4. D0.200

    0.200 doubles the required liquid mole fraction.

Reference: SCE–Qiyas Engineering Fundamentals – Chemical, Mass Transfer – CHE-T6-01..07 Diffusion, stage operations and efficiencies

07In a constant-volume batch reactor, a second-order reaction follows −r_A = kC_A². k = 0.50 L/(mol·min), C_A0 = 2.0 mol/L. What is C_A after 1.0 min?

Practice question Unit: Reaction Engineering

  1. A1.33 mol/L

    1.33 does not satisfy 1/C_A = 1/C_A0 + kt.

  2. B1.00 mol/L ✓ Correct answer

    1/C_A = 1/2 + 0.50×1 = 1, so C_A = 1.00 mol/L.

  3. C1.21 mol/L

    1.21 comes from applying a first-order exponential law.

  4. D0.400 mol/L

    0.400 would require a longer reaction time.

Reference: SCE–Qiyas Engineering Fundamentals – Chemical, Reaction Engineering – CHE-T7 Rate equations, kinetics and conversion

08An initially at-rest first-order process G(s) = 2/(5s + 1) receives a unit step at t = 0. What is the output after one time constant?

Practice question Unit: Process Control

  1. A2.00

    2.00 is the final output, reached asymptotically.

  2. B1.26 ✓ Correct answer

    At t = τ, y = 2(1−e⁻¹) ≈ 1.26.

  3. C0.736

    0.736 is the remaining difference from the final output.

  4. D0.632

    0.632 ignores the process gain of 2.

Reference: SCE–Qiyas Engineering Fundamentals – Chemical, Process Control – CHE-T8 Dynamics, controllers and stability

09Annual equivalent cost of a $100,000 investment over 10 years at 10% (no salvage)?

Practice question Unit: Process Economics

  1. A10,000 $/yr

    10000 divides principal by years but ignores interest.

  2. B14,903 $/yr

    14903 is not the 10-year, 10% capital-recovery payment.

  3. C11,000 $/yr

    11000 adds interest to one tenth of principal only.

  4. D16,275 $/yr ✓ Correct answer

    A = 100000[0.1(1.1)¹⁰/((1.1)¹⁰−1)] ≈ 16275 per year.

Reference: SCE–Qiyas Engineering Fundamentals – Chemical, Process Economics – CHE-T9 Cost estimation, time value of money and profitability

10For substances with additive effects, a worker has mixed exposures of 30 ppm of A (TLV 100 ppm) and 40 ppm of B (TLV 50 ppm). What is the combined exposure index?

Practice question Unit: Safety, Health, and Environment

  1. A0.300

    0.300 counts only exposure to A.

  2. B0.800

    0.800 counts only exposure to B.

  3. C1.10 ✓ Correct answer

    The additive index is 30/100 + 40/50 = 1.10, above 1.

  4. D0.467

    0.467 divides total concentration by total limits; add normalized fractions instead.

Reference: SCE–Qiyas Engineering Fundamentals – Chemical, Safety, Health, and Environment – CHE-T10 Process safety, hazards and environmental regulation

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