ECAT Pre Engineering Chemistry Chapter 8 MCQ Test With Answer

When rate of forward reaction is equal to rate of backward reaction, then the equilibrium established is called

• Chemical equilibrium A
• Static equilibrium B
• Dynamic equilibrium C
• None of these D

For which system does the equilibrium constant. K_c has units of

• 
  A
• 
  B
• 
  C
• 
  D

When a weak acid is dissolved in water or a weak base dissolved in water, then in both cases the conjugate acid base pair is produced. The ionization constants K_aand K_bof a pair are related with each other as

• K_a= K_b A
• K_a. K_b= K_w B
• K_a. K_w= K_b C
• K_b. K_w= K_a D

The avtive mass of 64 g of HI in a two litre flask would be

• 2 A
• 1 B
• 5 C
• 0.25 D

Law of mass action was given by :

• Guldberg and Waage. A
• Berkeley and Hartly. B
• Ramsay and Reyleigh. C
• Berthelot. D

The equilibrium constant in a reversible chemical reaction at a given temperature

• Depends on the initial concentration of the reactants A
• Depends on the concentration of one of the products at equilibrium B
• Does not depend on the initial concentration of rectants C
• It is characteristic of the reaction D

• 0.02 A
• 0.2 B
• 50 C
• 25 D

• 8 A
• 4 B
• 9 C
• 3 D

In the particular reaction for the valueK_{c 1 x}10^-25which statement is correct :

• Almost forward reaction is completed. A
• Amount of reactant is negligible as compared to product. B
• Amount of product is negligible as compared to reactant. C
• Amount of product is equal to amount of reactant. D

For the above reaction the relationship b/w k_c and k_p will be :

• K_p = K_cRT

  A

• Kp = K_c(RT)_-1

  B

• K_p = K_c(RT)_-2

  C

• K_c = K_p

  D

The concentration of reactants is increased by x, then equilibrium constant K becomes

• ln K/x A
• K/x B
• K + x C
• K D

• Complete conversion of A to B has taken place A
• Conversion of A to B is only 50% complete B
• Only 10% conversion of A to B has taken place C
• The rate of transformation of A to B is just equal to rate of transformation of B to A in the system D

• Shift reaction toward forward direction A
• Shift reaction backward B
• Lower the value of K_c C
• No change in reaction D

Ammonium carbonate when heated to 200°C gives a mixture of NH₃and CO₂vapour with a density of 13.0. What is the degree of dissociation of ammonia carbonate?

• 3/2 A
• 1/2 B
• 2 C
• 1 D

The rate of forward reaction is two times that of the reverse reaction at a given temperature and identical concentration, K equilibrium is

• 0.5 A
• 1.5 B
• 2.5 C
• 2.0 D

The rate at which a substance reacts is directly proportional to its active mass and the rate of reaction is directly proportional to the product of the active masses of reacting substances, is called

• Law of conservation of energy A
• Le-Chateliers principle B
• Law of mass action C
• None of these D

pH and pKa of the buffer are related by Henderson equation which is

• 
  A
• 
  B
• 
  C
• 
  D

The substance which increases rate of reaction but remains unchanged at the end of reaction is called :

• Catalyst. A
• Indicator. B
• Promoter. C
• Activator. D

In 1000 molecules of 0.001 M acetic acid the number of H⁺ions is 12.6, then its percentage of ionization is

• 1.33% A
• 1.26% B
• 12.6 C
• 1% D

• K_p> K_c A
• K_c> K_p B
• K_p= K_c C
• None of these D

In a reversible chemical reaction having two reactants in equilibrium, if the concentration of the reactants are doubled then the equilibrium constant will

• Also be doubled A
• Be halved B
• Becomes one fourth C
• Remains the same D

For which system does the equilibrium constant, kc has units of (concentration) ?

• N₂+3H_2-------2NH₃

  A

• H₂+L₂---------2HL

  B

• 2NO₂----------N₂O₄

  C

• 2HF--------H2+F₂

  D

• Le-chatlier's principle A
• Only adding catalyst B
• Decreasing pressure C
• Decreasing temperature D

Buffers having pH less than 7 are made

• Mixture of weak acid + salt of it with strong base A
• Mixture of weak acid + salt of it with weak base B
• Mixture of weak base + salt of it with strong acid C
• Mixture of weak base + salt of it with weak base D

• Reversible reaction A
• Irreversible reaction B
• Spontaneous reaction C
• None of these D

N₂ + 3H₂ ⇌2NH₃

The unit of K_c for tis reaction will be:

• mol² dm^-6

  A

• mol^-2 dm⁺⁶

  B

• mol dm^-3

  C

• mol^-1 dm⁺³

  D

In a reversible reaction, two substances are in equilibrium. If the concentration of each one is reduced to half, the equilibrium constant will be

• Reduced to half of its original value A
• Doubled B
• Same C
• Reduced to one fourth its original value D

• 0.5 A
• 4.0 B
• 2.5 C
• 0.25 D

When H₂and I₂are mixed and equilibrium is attained, then

• Amount of HI formed is equal to the amount of H₂dissociated A
• HI dissociation stops B
• The reaction stops completely C
• None of these D

• HF is stable and does not decompose even at 2000°C A
• HF is stable and slowly decomposes at 2000°C B
• HF is strong acid C
• HF produces equal moles of hydrogen and fluorine D