Practice Pakistan's most useful MCQs for competitive exams

What is the unit of the rate constant in a chemical reaction in which 10% of the reactant decomposes in one hour, 20% in two hours, 30% in three hours and so on ?

• (A)  Litre/mole.second
• (B)  Moles/litre.second
• (C)  Litre/mole
• (D)  Litre/second

Answer

Submitted By :Ali Uppal

Which of the following is an autocatalytic reaction ?

• (A)  Photochemical reactions
• (B)  Microbial fermentation reaction
• (C)  Enzyme fermentation reaction
• (D)  Ammonia synthesis reaction

Answer

Submitted By :Ali Uppal

An isothermal irreversible reaction is being carried out in an ideal tubular flow reactor. The conversion in this case will ______________ with decrease in space time?

• (A)  Increase
• (B)  Increase exponentially
• (C)  Decrease
• (D)  Remain unchanged

Answer

Submitted By :Ali Uppal

During manufacture of H2SO4, the oxidation of SO2 to SO3 by oxygen is an endothermic reaction. The yield of SO3 will be maximised, if the _____________________?

• (A)  Temperature is increased
• (B)  Pressure is reduced
• (C)  Temperature is increased and pressure is reduced
• (D)  Temperature is reduced and pressure is increased

Answer

Submitted By :Ali Uppal

From Arrhenius law, a plot of loge K versus 1/T gives a straight line with a slope of (-E/R). The unit of E/R is___________________?

• (A)  k cal
• (B)  k cal/°K
• (C)  °K
• (D)  k cal. °K

Answer

Submitted By :Ali Uppal

Pick the WRONG design guideline for a reactor in which the reactions, A → R (desired) and A → S (undesired) are to take place. The ratio of the reaction rates is rR/rS = (k1/k2). CA a-b ?

• (A)  Use high pressure and eliminate inerts, when a > b
• (B)  Avoid recycle, when a > b
• (C)  Use batch reactor or plug flow reactor, when a > b
• (D)  Use CSTR with a high conversion, when a > b

Answer

Submitted By :Ali Uppal

Holding time for flow reactors is _______________ the space time, for constant fluid density ?

• (A)  Double
• (B)  Triple
• (C)  Equal to
• (D)  None of these

Answer

Submitted By :Ali Uppal

Conversion increases with increase in temperature in case of a/an ______________ reaction?

• (A)  Autocatalytic
• (B)  Irreversible
• (C)  Reversible endothermic
• (D)  Reversible exothermic

Answer

Submitted By :Ali Uppal

Considering the endothermic dissociation of CaCO3 in a closed vessel (CaCO3 ⇌ CaO + CO2), the pressure of CO2 increases, if____________________?

• (A)  A catalyst is added
• (B)  The temperature is increased
• (C)  An inert gas is pumped keeping the temperature constant
• (D)  None of these

Answer

Submitted By :Ali Uppal

Thermodynamic equilibrium constant in a system is affected by___________________?

• (A)  Inerts
• (B)  Pressure
• (C)  Temperature
• (D)  All

Answer

Submitted By :Ali Uppal