A physician wishes to prepare a buffer solution at pH=3.58 that efficiently resist changes in pH yet contains only small concetration of the buffering agents. Which one of the following weak acid together with its sodium salt would be best to use ?           [1997]

1. m-chlorobenzoic acid (pKa = 3.98)

2. p-chlorocinnamic acid (pKa = 4.41)

3. 2,5-dihydroxy benzoic acid (pKa = 2.97)

4. Acetoacetic acid (pKa = 3.58)

Subtopic:  Buffer |
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One mole of ethyl alcohol was treated with one mole of acetic acid at 25°C. 2/3 of the acid changes into ester at equilibrium. The equilibrium constant for the reaction will be:

1. 1                   

2. 2

3. 3                   

4. 4

Subtopic:  Introduction To Equilibrium |
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For a given solution pH = 6.9 at 60°C, where Kw=10-12. The solution is:

1. acidic                                         

2. basic

3. neutral                                         

4. unpredictable

Subtopic:  pH calculation |
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In a buffer solution containing equal concentration of B- and H B, the Kb for B- is 10-10. The pH of buffer solution is 

1. 10

2. 7

3. 6

4. 4

Subtopic:  Buffer |
 66%
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Aqueous solution of acetic acid contains                                                   

1. CH3COO- and H+

2. CH3COO-, H3O+ and CH3COOH

3. CH3COO-, H3O+ and H+

4. CH3COOH, CH3COO- and H+

Subtopic:  Ionisation Constant of Acid, Base & Salt |
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The equilibrium, 2SO2 (g) + O2 (g2SO3 (g)

shifts forward if:

1. a catalyst is used

2. an absorbent is used to remove SO3 as soon as it is formed

3. small amounts of reactants are used

4. none of the above

Subtopic:  Le Chatelier's principle |
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The pH of blood is maintained by CO2 by and H2CO3 in the body and chemical constituents of blood. This phenomenon is called:

1. colloidal                           

2. buffer action

3. acidic                               

4. salt balance

Subtopic:  Buffer |
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Incorrect statement among the following is: 

1. Addition of one drop of concentrated HCl in NH4OH solution decreases pH of the solution.

2. A solution of the mixture of one equivalent of each of CH3COOH and NaOH has a pH of 7

3. pH of pure neutral water is not zero.

4. A cold and concentrated H2SO4 has lower H+ ion concentration than a dilute solution of H2SO4 

Subtopic:  pH calculation |
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At temperature T, a compound AB2 (g) dissociates according to the reaction 2AB22AB(g) +B2(g) with a degree of  dissociation x, which is small compared with unity. The expression for Kp, in terms of x and the total pressure P , is:

1. Px3/2                                 

2. Px2/3

3. Px3/3                                 

4. Px2/2

Subtopic:  Kp, Kc & Factors Affecting them |
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The rate constants for forward and backward reaction of hydrolysis is ester are 1.1 x10-2 and 1.5x10-3 per minute. Equilibrium constant for the reaction,                                                              

 CH3COOC2H5 + H+  CH3COOH + C2H5OH is

1. 4.33           

2. 5.33           

3. 6.33         

4. 7.33

Subtopic:  Introduction To Equilibrium |
 78%
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