All Free Chemical Engineering MCQs with Answers

• A. Either A. or B., depends on order of reaction
• B. Less
• C. Same
• D. More

Explanation: An exothermic reaction releases energy, so the products lie at a lower energy level than the reacting substances.

• A. A highly exothermic reaction is to be controlled
• B. All A., B., and C.
• C. A gas is to be reacted with liquid (e.g. hydrogenation of fat)
• D. Undesirable side reaction (at high concentration of one of the reactants) is to be avoided

Explanation: Semibatch operation permits gradual addition of a reactant, helping control heat release and preventing high reactant concentrations that…

• A. CA0/K
• B. CA0/2K
• C. 0.693/K
• D. 1/K

Explanation: For a zero-order reaction, the concentration relation is C_A=C_A0−kt. Setting C_A=C_A0/2 gives t_1/2=C_A0/(2k), unlike a first-order…

• A. Pore
• B. Ash layer
• C. Film
• D. None of these

Explanation: At very high temperature, the chemical reaction is usually fast, so transport through the external gas film becomes the limiting step.

• A. Pressure and temperature only
• B. Temperature and composition only
• C. Pressure and composition only
• D. Pressure, temperature and composition

Explanation: Homogeneous reaction rates can change with composition through concentration, with temperature through the rate constant, and with…

• A. Equal in size
• B. Of different sizes
• C. Of such size that the ratio of their volumes is < 5
• D. None of these

Explanation: For two CSTRs carrying out a first-order reaction, minimizing total volume requires equal concentration-ratio reductions in the two…

• A. Gas film
• B. Ash
• C. Chemical reaction
• D. None of these

Explanation: Carbon combustion produces gaseous products such as CO or CO₂, not a solid ash layer that must be penetrated.

• A. 0
• B. 1
• C. 2
• D. 3

Explanation: With rate proportional to C_A^n, doubling concentration changes the rate by 2^n.

• A. Used to convert heat energy into
• B. Accompanied with emission of
• C. Catalysed by
• D. Initiated by

Explanation: Photochemical reactions obtain the initiating energy from absorbed radiation, so light starts the reaction by exciting molecules or…

• A. k2 CB0 > k1 CA0
• B. k CA0 > k2.CB0
• C. CB0 > CA0
• D. CA0 > CB0

Explanation: For A → B → C, B initially rises only when its formation rate, k₁C_A0, exceeds its consumption rate, k₂C_B0.

• A. More than
• B. Same as
• C. Less than
• D. Data insufficient; can't be predicted

Explanation: A first-order reaction has a constant half-life, t₁/₂ = ln 2/k, independent of the starting concentration.

• A. Phenol
• B. Naphthalene
• C. Isopropanol
• D. Ethyl benzene

Explanation: Isopropanol undergoes catalytic dehydrogenation to form acetone and hydrogen: (CH₃)₂CHOH → (CH₃)₂CO + H₂.

• A. Phenol
• B. Ethyl alcohol
• C. Cumene
• D. Styrene

Explanation: Dehydrogenation removes hydrogen from ethylbenzene and forms styrene, an important monomer used to make polystyrene.

• A. Formaldehyde
• B. Phenol
• C. Acetone
• D. Maleic anhydride

Explanation: Catalytic oxidation-dehydrogenation of methanol converts it to formaldehyde, commonly using a silver or metal-oxide catalyst.

• A. Dehydration
• B. Reduction
• C. Oxidation
• D. Polymerisation

Explanation: Biological treatment oxidises biodegradable organic matter, mainly through microbial activity, converting it into carbon dioxide, water…

• A. -5 to 0
• B. 5 to 10
• C. 75 to 80
• D. 30 to 50

Explanation: Many fermentation processes use dilute nutrient solutions and are carried out near the moderate-temperature range of about 30 to 50°C.

• A. Vanadium
• B. Nickel
• C. Alumina
• D. Iron

Explanation: Commercial oxidation of ortho-xylene to phthalic anhydride uses vanadium pentoxide, usually supported on a carrier.

• A. Autothermal
• B. Trickle bed
• C. Plug flow
• D. None of these

Explanation: Vegetable-oil hydrogenation commonly uses a trickle-bed reactor, where liquid oil and hydrogen pass over a fixed bed of catalyst…

• A. Fischer-Tropsch process
• B. Ostwald's process of HNO3 manufacture
• C. Hydrogenation of oil
• D. Shift conversion

Explanation: The Ostwald process oxidizes ammonia over a platinum-rhodium gauze catalyst, not nickel.

• A. Ni
• B. Pt
• C. V2O5
• D. Cr

Explanation: Vanadium pentoxide, V₂O₅, catalyses the vapor-phase oxidation of benzene to maleic anhydride.