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 169 of 350
- A. Dehydrogenation of naphthenes
- B. Hydrogenation of naphthenes
- C. Hydrocracking of paraffins
- D. Saturation of olefins
Explanation: Catalytic reforming raises octane mainly by converting naphthenes into aromatic hydrocarbons with release of hydrogen, a dehydrogenation…
Correct answer: Dehydrogenation of naphthenes3362. Gasoline yield in catalytic reforming of naphtha may be about _________________ percent by weight?
- A. 85
- B. 65
- C. 50
- D. 98
Explanation: Catalytic reforming of naphtha normally gives a high reformate or gasoline yield, commonly around 80 to 90 percent by weight.
Correct answer: 85- A. Lighter paraffins
- B. Olefins and aromatics
- C. Stabilised gasoline
- D. Diesel
Explanation: Pyrolysis cracks kerosene or natural gasoline at high temperature into smaller unsaturated molecules and ring compounds, producing mainly…
Correct answer: Olefins and aromatics- A. Alumina
- B. Nickel
- C. Silica gel
- D. Sulphuric acid
Explanation: Sulphuric acid is a liquid acid catalyst commonly used in alkylation to combine light olefins with isoparaffins.
Correct answer: Sulphuric acid- A. An endothermic reaction
- B. An exothermic reaction
- C. Favoured at very low temperature
- D. None of these
Explanation: Cracking breaks large hydrocarbon molecules into smaller ones and requires heat to rupture their bonds, so it is endothermic.
Correct answer: An endothermic reaction- A. Less than 90% promotes polymerisation
- B. Both A. and B.
- C. More than 98% promotes cracking
- D. Neither A. nor B.
Explanation: Acid that is too dilute, below about 90%, encourages polymerisation of olefins, while excessively concentrated acid can promote…
Correct answer: Both A. and B.- A. H2SO4
- B. H3PO4
- C. AlCl3
- D. HF
Explanation: Aluminium chloride, usually with hydrogen chloride, is the classical catalyst system for hydrocarbon isomerisation.
Correct answer: AlCl3- A. Olefins into paraffins
- B. Naphthenes into paraffin
- C. Naphthenes into olefins
- D. Naphthenes into aromatics
Explanation: In catalytic reforming, cycloalkanes or naphthenes undergo dehydrogenation to form aromatic hydrocarbons, often with hydrogen as a…
Correct answer: Naphthenes into aromatics- A. Dehydrogenation of lower paraffins
- B. Dehydrogenation of Naphthene
- C. Dehydrocyclization of higher paraffins
- D. Isomerisation of paraffins
Explanation: Catalytic reforming favorably dehydrogenates naphthenes, dehydrocyclizes suitable paraffins and isomerizes hydrocarbons to raise octane…
Correct answer: Dehydrogenation of lower paraffins- A. 10 atm & 500°C
- B. 2 atm & 500°C
- C. 30 atm & 200°C
- D. 50 atm & 750°C
Explanation: Fluid catalytic cracking commonly uses temperatures near 500°C and relatively low pressures, around 1–3 atm, because cracking is favoured…
Correct answer: 2 atm & 500°C- A. Gasoline obtained has a very low octane number
- B. Pressure & temperature is very high
- C. Gasoline obtained has very high amount of gum forming compounds
- D. Gasoline obtained has very high aromatic content
Explanation: Catalytic cracking promotes dehydrogenation, cyclisation and aromatisation, so its gasoline generally has a high octane number and…
Correct answer: Gasoline obtained has very high aromatic content- A. Non-elementary
- B. Multiple
- C. Autocatalytic
- D. Elementary
Explanation: For an elementary reaction, the rate equation follows directly from the stoichiometric equation.
Correct answer: Non-elementary- A. Is independent of temperature
- B. Both B. and C.
- C. Depends on the nature of the reactants
- D. Varies with temperature
Explanation: The rate constant changes with temperature according to the Arrhenius relationship and also depends on the reacting species and reaction…
Correct answer: Both B. and C.- A. 1
- B. 2
- C. 3
- D. 4
Explanation: For a second-order reaction, the time required for a fixed fractional conversion is proportional to 1/C₀.
Correct answer: 2- A. Nature of the reactants
- B. Concentration of the reactants
- C. Temperature at which the reaction is carried
- D. All A., B. and C.
Explanation: Reaction velocity is affected by the chemical nature of the reactants, their concentrations, and temperature.
Correct answer: All A., B. and C.- A. Catalytic cracking
- B. Methanol synthesis
- C. Ammonia synthesis
- D. Oxidation of sulphur
Explanation: Catalytic cracking requires heat to break large hydrocarbon molecules into smaller ones, so it is endothermic.
Correct answer: Catalytic cracking- A. 5°C
- B. 10°C
- C. 20°C
- D. 100°C
Explanation: At 50% conversion, heat released is 0.5 kJ per mole initially present. The adiabatic temperature rise is ΔT = 0.5/0.050 = 10 K, which is…
Correct answer: 10°C- A. Series of CSTR
- B. Plug flow reactor
- C. Backmix reactor
- D. PFR in series
Explanation: When high reactant concentration improves yield, backmixing is undesirable because a CSTR operates throughout at the lower exit…
Correct answer: Backmix reactor- A. 100
- B. 97.5
- C. 95
- D. 2.5
Explanation: Formation of 95 kmol/h ethylene consumes 95 kmol/h ethanol, while 2.5 kmol/h diethyl ether consumes 5 kmol/h ethanol.
Correct answer: 100- A. Mixing takes place in axial direction only
- B. Residence time is constant
- C. Condition similar to plug flow reactor exists
- D. Velocity of reaction can be controlled
Explanation: A semi-batch reactor permits controlled addition or removal of reactants during operation, so the reaction rate can be adjusted through…
Correct answer: Velocity of reaction can be controlled