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 263 of 350
5241. A high pressure boiler generates steam at a pressure greater than _____________________ kg/cm2 ?
- A. 10
- B. 30
- C. 50
- D. 80
Explanation: Boilers generating steam above about 80 kg/cm2 are commonly classified as high-pressure boilers.
Correct answer: 80- A. Soap solution
- B. Using chemical reagents
- C. Its smell
- D. Sulphur stick, which on detection gives white smoke
Explanation: A sulfur stick produces sulfur dioxide, which reacts with leaking ammonia to form visible white ammonium-salt fumes.
Correct answer: Sulphur stick, which on detection gives white smoke- A. None of these
- B. Diameter & length of the pipe
- C. Temperature of hot pipe surface & that of air in the room
- D. Emissivity of pipe surface
Explanation: Radiation and natural-convection heat loss depend on surface emissivity, pipe geometry, and the temperature difference between the pipe…
Correct answer: None of these- A. Grashoff number
- B. Grashoff number & Prandtl number
- C. Reynolds number
- D. Grashoff number & Reynolds number
Explanation: The transition criterion in free convection is expressed through the Rayleigh number, Ra = Gr·Pr, so both the Grashof and Prandtl numbers…
Correct answer: Grashoff number & Prandtl number- A. None of these
- B. Tube carrying hot flue gases are immersed in a pool of water
- C. Tubes are placed in vertical position
- D. Water passes through tubes and flue gases around it
- E. Answer: Option A
Explanation: In a water-tube boiler, water circulates inside the tubes while hot flue gases flow around their outer surfaces.
Correct answer: Water passes through tubes and flue gases around it- A. All 'A', 'B' & 'C'
- B. Area
- C. Nature
- D. Temperature
Explanation: For thermal radiation, the wavelength of maximum emission is fixed by the surface temperature according to Wien's displacement law.
Correct answer: Temperature- A. Conduction in air
- B. Forced convection in air
- C. Free convection in air
- D. Boiling
Explanation: Still air has very low thermal conductivity, so conduction through air provides less heat transfer than either natural or forced…
Correct answer: Conduction in air- A. (ε1 + ε2)/ε1.ε2
- B. ε1.ε2
- C. ε1.ε2/(ε1 + ε2 - ε1.ε2)
- D. ε1 + ε2
Explanation: For two infinite facing gray surfaces, the radiation exchange factor is the reciprocal of the two surface resistances and the space…
Correct answer: ε1.ε2/(ε1 + ε2 - ε1.ε2)- A. More
- B. Less
- C. Much more
- D. Equal
Explanation: For fixed terminal temperature differences, the LMTD calculation uses the same two end differences for both flow arrangements.
Correct answer: Equal- A. Density
- B. Thermal diffusivity
- C. Viscosity
- D. Thermal conductivity
Explanation: As temperature rises at approximately constant pressure, air expands and its density decreases.
Correct answer: Density- A. High temperature heating medium (a petroleum product)
- B. Product of coal tar distillation
- C. Very heat sensitive material
- D. None of these
Explanation: Dowtherm is a high-temperature heat-transfer fluid used where water or steam cannot provide the required operating temperature.
Correct answer: High temperature heating medium (a petroleum product)5252. A reduction in thermal resistance during heat transfer does not occur in the___________________?
- A. Convection heat transfer by stirring the fluid and cleaning the heating surface
- B. Radiation heat transfer by increasing the temperature and reducing the emissivity
- C. conductivity
- D. Conduction heat transfer by reduction in the material thickness and increase in the thermal
- E. None of these
Explanation: For radiation, lowering emissivity lowers the radiation heat-transfer coefficient and increases thermal resistance, so it does not produce…
Correct answer: Radiation heat transfer by increasing the temperature and reducing the emissivity- A. Transition
- B. Nucleate
- C. Film
- D. All modes of
Explanation: Fins are advantageous in film boiling because the vapour film creates high thermal resistance and gives a relatively low heat-transfer…
Correct answer: Film- A. 25
- B. 45
- C. 65
- D. 20
Explanation: Very inefficient or older steam boilers may have thermal efficiencies near 20%, although modern boilers are usually much more efficient.
Correct answer: 20- A. High heat capacity
- B. Both B. and C.
- C. High thermal conductivity
- D. Low heat capacity
Explanation: A cooking vessel should have high thermal conductivity so heat spreads quickly and uniformly, but low heat capacity so it does not require…
Correct answer: Both B. and C.- A. Bomb
- B. Junker's
- C. Throttling
- D. Boy's
Explanation: A throttling calorimeter determines steam dryness from the pressure and temperature after throttling, where the process is approximately…
Correct answer: Throttling- A. All 'A', 'B' & 'C'
- B. Wet bulb temperature=dew point temperature
- C. Saturation temperature=dew point temperature
- D. Wet bulb temperature=dry bulb temperature
Explanation: At 100% relative humidity, the air is saturated, so dry-bulb, wet-bulb and dew-point temperatures are all equal.
Correct answer: All 'A', 'B' & 'C'- A. 80.38
- B. 80
- C. 79.62
- D. 78.51
Explanation: Relative humidity gives a vapour partial pressure of 0.80 × 17.5 = 14 mm Hg.
Correct answer: 79.62- A. Nature of the liquid
- B. Temperature of the liquid
- C. Nature of the gas
- D. Total pressure
Explanation: For an ideal gas saturated with vapour, the vapour partial pressure is fixed by the liquid's vapour pressure at the temperature, and its…
Correct answer: Nature of the gas- A. Henry's
- B. Raoult's
- C. Amagat's
- D. None of these
Explanation: Henry’s law states that, at dilute concentrations, the equilibrium dissolved concentration or mole fraction of a gas is proportional to…
Correct answer: Henry's