Practice Pakistan's most useful MCQs for competitive exams

A first order reaction A → B occurs in an isothermal porous catalyst pellet of spherical shape. If the concentration of A at the centre of the pellet is much less than at the external surface, the process is limited by__________________?

• (A)  Diffusion within the pellet
• (B)  Reaction
• (C)  External mass transfer
• (D)  None of the above

Answer

Submitted By :Ali Uppal

The use of space time is preferred over the mean residence time in the design of a/an____________________?

• (A)  Batch reactor
• (B)  Ideal tubular-flow reactor
• (C)  Slurry reactor
• (D)  CSTR

Answer

Submitted By :Ali Uppal

For a packed bed reactor; the presence of a long tail in the residence time distribution curve is an indication of ?

• (A)  Ideal plug flow
• (B)  Bypass
• (C)  Dead zone
• (D)  Channelling

Answer

Submitted By :Ali Uppal

Overall rate of reaction in a heterogeneous catalytic reaction depends upon the mass and energy transfer from the fluid to solid surface and its rate of reaction is usually ________________ the concentration of catalyst, if it does not entail a chain mechanism?

• (A)  Proportional to
• (B)  Independent of
• (C)  Inversely proportional to
• (D)  Proportional to the square of

Answer

Submitted By :Ali Uppal

Fractional conversion _________________ for an exothermic reversible chemical reaction, when the temperature is maximum?

• (A)  Increases
• (B)  Remains unchanged
• (C)  Decreases
• (D)  Unpredictable from the data

Answer

Submitted By :Ali Uppal

For identical flow rate and feed composition, X plug flow reactors (PER) in series with a total volume V gives the same conversion as single_______________?

• (A)  CSTR of volume V
• (B)  PFR of volume V
• (C)  CSTR of volume V/X
• (D)  PFR of volume V/X

Answer

Submitted By :Ali Uppal

The irreversible reaction, X → Y, is the special case of the reversible reaction, X ⇌ Y, in which the _____________________?

• (A)  Equilibrium constant is infinite
• (B)  Fractional conversion of ‘A’ at equilibrium is unity
• (C)  Concentration of ‘A’ at equilibrium is zero
• (D)  All

Answer

Submitted By :Ali Uppal

Half life period of decomposition of a liquid ‘A’ by irreversible first order reaction is 12 minutes. The time required for 75% conversion of ‘A’ is _____________ minutes?

• (A)  18
• (B)  24
• (C)  6
• (D)  12

Answer

Submitted By :Ali Uppal

The fractional volume change between no conversion and complete conversion, for the isothermal gas phase reaction, 2A → R, is___________________?

• (A)  0.5
• (B)  -0.5
• (C)  1
• (D)  1.5

Answer

Submitted By :Ali Uppal

For a heterogeneous catalytic reaction, A + B → C, with equimole feed of A and B, the initial rate – rA0 is invariant with total pressure. The rate controlling step is______________________?

• (A)  Surface Kc/(1 + TS) reaction between absorbed A and B in the gas phase
• (B)  Surface reaction between absorbed A and absorbed B
• (C)  Surface reaction between A in the gas phase and absorbed B
• (D)  Desorption of C

Answer

Submitted By :Ali Uppal