Practice Pakistan's most useful MCQs for competitive exams

Molecularity of an elementary reaction, P + Q → R + S is ____________________?

• (A)  1
• (B)  2
• (C)  3
• (D)  4

Answer

Submitted By :Ali Uppal

Effectiveness factor E. of a catalyst pellet is defined as, E = (actual rate within pore of the catalyst)/(rate if not snowed by pore diffusion), Effectiveness factor for a first order reaction is given by (where, T = Thiele modulus) ___________________?

• (A)  tan hT/T
• (B)  tan T/T
• (C)  tan hT/tan T
• (D)  None of these

Answer

Submitted By :Ali Uppal

Photo-chemical reactions occur in presence of ___________________?

• (A)  Sunlight
• (B)  Darkness
• (C)  Solid catalysts
• (D)  Monochromatic radiation only

Answer

Submitted By :Ali Uppal

The conversion of a reactant, undergoing a first order reaction, at a time equal to three times the half life of the reaction is ?

• (A)  0.875
• (B)  0.5
• (C)  0.425
• (D)  Data insufficient to calculate

Answer

Submitted By :Ali Uppal

The heat of reaction__________________?

• (A)  Depends on the pressure only
• (B)  Depends on the mechanism of reaction only
• (C)  Depends on both pressure and mechanism of reaction
• (D)  Is independent of the mechanism of reaction

Answer

Submitted By :Ali Uppal

Concentration of the limiting reactant (with initial concentration of a moles/litre) after time t is (a-x). Then ‘t’ for a first order reaction is given by____________________?

• (A)  k. t = ln a/(a – x)
• (B)  k. t = x/a (a – x)
• (C)  k. t = ln (a – x)/a
• (D)  k. t = ln a (a – x)/x

Answer

Submitted By :Ali Uppal

What is the maximum possible value of FR(mole/sec.) ?

• (A)  1/3
• (B)  1/2
• (C)  2/3
• (D)  2

Answer

Submitted By :Ali Uppal

A second order reaction of the form A + B → C is called a pseudo-first order reaction, when____________________?

• (A)  CA0 = CB0
• (B)  CA0 > CB0
• (C)  CB0 > CA0
• (D)  CB0 ≥ CB0

Answer

Submitted By :Ali Uppal

Pure A in gas phase enters a reactor 50% of this A is converted to B through the reaction, A → 3B. Mole fraction of A in the exit stream is______________________?

• (A)  1/2
• (B)  1/3
• (C)  1/4
• (D)  1/5

Answer

Submitted By :Ali Uppal

A chemical reaction occurs when the energy of the reacting molecules is __________________ the activation energy of the reaction?

• (A)  Less than
• (B)  Equal to
• (C)  More than
• (D)  Equal to or more than

Answer

Submitted By :Ali Uppal