ECAT Pre Engineering Chemistry Chapter 8 MCQ Test With Answer

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

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

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

• 
  A
• 
  B
• 
  C
• 
  D

pH of the human blood which is essentially maintained constant due to carbonates, biocarbonates, phosphates etc., is

• 7.00 A
• 7.25 B
• 7.35 C
• 7.47 D

Which of the following is a characteristic of a reversible reaction?

• It never proceeds to completion A
• It can be influenced by a catalyst B
• It proceeds only in the forward direction C
• Number of moles of reactants and products are equal D

In an exothermic reaction, a 10° rise in temperature will

• Decrease the value of equilibrium constant A
• Double the value of K_c B
• Not produce any change in K_c C
• Produce some increase in K_c D

The best buffer is prepared when molar concentrations of the salt and acid are equal, then its pH and pKa value are related

• pH = pKa A
• pH < pKa B
• pH > pKa C
• pH x pKa = 14 D

1.1 mol of A is mixed with 2.2 mol of B and the mixture is kept in on litre flask till the equilibrium is reached. At equilibrium, 0.2 mol of C is formed. If the equilibrium reaction is A+2B 2C+D, the value of equilibrium constant is

• 0.002 A
• 0.004 B
• 0.001 C
• 0.003 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

• 0.60 A
• 1.67 B
• 0.66 C
• 2.6 D

• Equal volumes of N₂and H₂are reacting A
• Equal masses of N₂and H₂are reacting B
• The reaction has stopped C
• The same amount of ammonia is formed as is decomposed into N₂and H₂ D

Two moles of HI was heated in a sealed tube at 440°C till the equilibrium was reached. HI was found to be 22% decomposed. The equilibrium constant for dissociation is

• 0.282 A
• 0.0796 B
• 0.0199 C
• 1.99 D

• The value of K_pfalls with rise in temperature A
• The value of K_pfalls with increasing pressure B
• Addition of V₂O₅catalyst increase the concentration of SO₃ C
• The value of K_pis equal to K_c D

• Increases A
• Decreases B
• Remains same C
• Cannot be predicted D

• Initial concentration of acetic acid A
• Initial concentration of ethyl acetate B
• Equilibrium concentration of acetic acid C
• Equilibrium concentration of ethyl acetate D

Hydrogen gas and iodine vapours combine to form Hl at 425°C, the same composition of mixture is present if we start with decomposition of Hl. It suggests

• A static equilibrium A
• Law of mass action B
• A dynamic equlibrium C
• Irreversible reaction 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

If the difference of pKa values of the two acids is 2, then

• Acid with smaller pKa is 10 times stronger acid A
• Acid with greater pKa is 10 times stronger acid B
• Acid with smaller pKa is 100 times stronger acid C
• Acid with greater pKa is 100 times stronger acid D

• 450°C A
• 250°C B
• 850°C C
• 1000°C D

K_avalue of HF acid is 6.7 x 10^-15the acid is a

• Weak acid A
• Moderately strong acid B
• Strong acid C
• Very weak acid D

N₂3H₂⇌ 2NH₃

_{Which of the following change will favorthe formation of more}NH₃at equilibrium in above reaction :

• By adding NH_3. A
• By removingH_2. B
• By decreasing pressure. C
• By increasing pressure. D

• Forward A
• Backward B
• Already in equilibrium C
• K_cis never less D

ph of the buffer CH₃COOh + CH₃COONa is 3.76. If the mixture contains 1 molar acetic acid and 0.1 molar sodium acetate, then pKa of this buffer is

• 3.76 A
• 4.76 B
• 5.76 C
• 6.76 D

The value of K_pis greater than K_cfor a gaseous reaction when

• Number of molecules of products is greater than the reactants A
• Number of molecules of reactants is greater than those of products B
• Number of molecules of reactants and products equal C
• Catalyst is added D

For which system does the equilibrium constant, KC has units of concentration

• 
  A
• 
  B
• 
  C
• 
  D

• Moles per dm³ A
• Partial pressures B
• Number of moles C
• Mole fractions D

The rate of reaction :

• Remain same as reaction proceeds. A
• May decrease or increase as reaction proceeds . B
• Increase as reaction proceeds. C
• Decreases as reaction proceeds. D

Almost forward reaction is complete when value of k_{c :}

• Neither larger nor very small. A
• Very small. B
• Very large. C
• Negligible. D

• Forward reaction is favoured A
• Backward reaction is favoured B
• No effect C
• None of the above D