A chemist wishes to prepare a buffer solution of pH = 2.90 that e

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 Multiple Choice QuestionsMultiple Choice Questions

741.

For the following equilibrium, N2O4 2NO2 in the gaseous phase, NO2 is 50% of the total volume when equilibrium is set up. Hence, per cent of dissociation of N2Ois

  • 50%

  • 25%

  • 66.66%

  • 33.33%


742.

Of the given anions, the strongest Bronsted base is

  • ClO-

  • ClO3-

  • ClO2-

  • ClO4-


743.

At equilibrium, if KP = 1, then

  • G° > 1

  • G° < 1

  • G° = 0

  • G° = 1


744.

Which of the following is most acidic?

  • H2O

  • H2S

  • H2Se

  • H2Te


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745.

1 mL of 0.01 N HCl is added to 999 mL solution of 0.1 N Na2SO4. The pH of the resulting solution will

  • 2

  • 7

  • 5

  • 1


746.

The equilibrium constants for the reaction,

Br2  2Br → 1

at 500 K and 700 K are 1 × 10-10 and 1 × 10-5 respectively. The reaction is

  • endothermic

  • exothermic

  • fast

  • slow


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747.

A chemist wishes to prepare a buffer solution of pH = 2.90 that efficiently resists a change in pH yet contains only small concentration of buffering agents which one of the following weak acid along with its salt would be best to use 

  • m-chlorobenzoic acid (pKa = 3.98)

  • Acetoacetic acid (pKa = 3.58)

  • 2 5-dihydrobenzoic acid (pKa = 2.97)

  • p-chlorocmanic acid (pKa = 4.41)


C.

2 5-dihydrobenzoic acid (pKa = 2.97)

The buffer solution to be made should effectively resists a change in pH, i.e., should have a higher buffer capacity.

Buffer capacity (Φ) = No. of moles of acid or base added to 1LChange in pH

By one of any two ways, we can obtain it,

(i) The higher the concentration of the components of a buffer mixture, the greater will be the buffer capacity But, the condition is to maintain a small concentrations of buffering components.

(ii) Buffer capacity of a buffer is maximum when the concentration of the weak acid and its salt are equal, i.e. [salt] = [acid].

 pH = pKa + log [salt][acid]

         = pKa + log 1 (as [Salt] = [acid])

    pH = pKa = 2.9

As, 2, 5-dihydrobenzoic acid has pKa value = 2.97, hence, it is the best choice for chemist to prepare buffer solution.


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748.

NaOH is a strong base. What will the be pH of 5.0 × 10-2 M NaOH solution? (log 2 = 0.3)

  • 14.00

  • 13.70

  • 13.00

  • 12.70


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749.

The equilibrium constants of the reactions

SO2(g) + 12O2(g)  SO3(g) and 2SO2(g) + O2(g)  2SO3(g) are K1 respectively. The relationship between K1 and K2 will be

  • K12=K2

  • K2 = √K1

  • K1= K2

  • K23 = K1


750.

The value of Kc for the dissociation reaction, H2 (g)  2H (g) is 1.2 × 10-42

This equilibrium mixture contains mainly

  • H2 (g)

  • H (g) atom

  • 1.1 M mixture of H2 and H

  • 1.2 M mixture of H2 and H


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