Ionic Equilibria, Buffers and Solubility - Chemical Equilibria - Life Sciences Previous Year Questions

1

2007 · Life Sciences · Chemical Equilibria · Ionic Equilibria, Buffers and Solubility

Life Sciences (XL) 2007

The acid dissociation constant of a weak acid HA is 10^-2. A 0.20 M solution of the acid HA also contains 0.10 M of salt MA₂. The pH of the solution is

A

0.69

B

1.0

C

2.85

D

5.0

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2

2007 · Life Sciences · Chemical Equilibria · Ionic Equilibria, Buffers and Solubility

Life Sciences (XL) 2007

Suppose ΔG denotes the free-energy change for the reaction A + B ⇌ C + H⁺ at pH 5, all other conditions being the same as the standard conditions specified above. Then

A

ΔG = ΔG°'

B

ΔG = ΔG°' + 11.5 RT

C

ΔG = ΔG°' + 4.6 RT

D

ΔG = ΔG°' + 16.1 RT

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3

2008 · Life Sciences · Chemical Equilibria · Ionic Equilibria, Buffers and Solubility

Life Sciences (XL) 2008

The pH of a \(10^{-8}\) molar hydrochloric acid solution is

A

exactly 8

B

between 7 and 8

C

exactly 7

D

between 6 and 7

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4

2008 · Life Sciences · Chemical Equilibria · Ionic Equilibria, Buffers and Solubility

Life Sciences (XL) 2008

An aqueous mixture solution is prepared which contains 0.1 M of \(KCl\) and 0.1 M \(KI\). To this solution, a drop of 0.01 M aqueous solution of \(AgNO_3\) is added.
Which of the following statement is correct?

A

A precipitate forms which is primarily AgI.

B

A precipitate forms which is primarily AgCl.

C

A precipitate forms which has equimolar amounts of AgCl and AgI.

D

There will be no precipitation, as there is no common ion between potassium and silver salts.

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5

2009 · Life Sciences · Chemical Equilibria · Ionic Equilibria, Buffers and Solubility

Life Sciences (XL) 2009

Equal volumes of two buffers of pH 4 and pH 6 of identical ionic strengths are mixed. The resultant pH is

A

close to 4.

B

close to 5.

C

close to 6.

D

exactly 5.

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6

2010 · Life Sciences · Chemical Equilibria · Ionic Equilibria, Buffers and Solubility

Life Sciences (XL) 2010

For a dilute solution of phosphorous acid in a pH 5 buffer, the predominant species is

A

H₃PO₃

B

H₂PO₃⁻

C

HPO₃²⁻

D

PO₃³⁻

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7

2011 · Life Sciences · Chemical Equilibria · Ionic Equilibria, Buffers and Solubility

Life Sciences (XL) 2011

H₂S is passed through an aqueous solution containing all the four metal ions. The metal ion that precipitates first is

A

Fe²⁺

B

Zn²⁺

C

Cu²⁺

D

Hg²⁺

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8

2011 · Life Sciences · Chemical Equilibria · Ionic Equilibria, Buffers and Solubility

Life Sciences (XL) 2011

The concentration of S²⁻, at which FeS begins to precipitate from the mixture having 0.1 M Fe²⁺ is

A

1.0 × 10⁻¹⁷ M

B

1.0 × 10⁻¹⁸ M

C

1.0 × 10⁻¹⁹ M

D

1.0 × 10⁻²⁰ M

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9

2012 · Life Sciences · Chemical Equilibria · Ionic Equilibria, Buffers and Solubility

Life Sciences (XL) 2012

The value of ionic product of water changes with temperature. It is 1 × 10^-14 at 25 °C and 1 × 10^-13 at 60 °C. The CORRECT statement with respect to ΔH and ΔS is

A

ΔH is negative and ΔS is negative

B

ΔH is positive and ΔS is zero

C

ΔH is positive and ΔS is negative

D

ΔH is negative and ΔS is positive

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10

2012 · Life Sciences · Chemical Equilibria · Ionic Equilibria, Buffers and Solubility

Life Sciences (XL) 2012

The value of K_a of acetic acid is 1.7 × 10^-5 mol/dm³. The pH of a buffer solution prepared by mixing 100 ml of 0.1 M acetic acid with a solution of 100 ml of 0.2 M sodium acetate is

A

4.1

B

4.5

C

5.1

D

5.5

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11

2013 · Life Sciences · Chemical Equilibria · Ionic Equilibria, Buffers and Solubility

Life Sciences (XL) 2013

If \( 3 \leq X \leq 5 \) and \( 8 \leq Y \leq 11 \) then which of the following options is TRUE?

A

\(\frac{3}{5} \leq \frac{X}{Y} \leq \frac{8}{5} \)

B

\(\frac{3}{11} \leq \frac{X}{Y} \leq \frac{5}{8} \)

C

\(\frac{3}{11} \leq \frac{X}{Y} \leq \frac{8}{5} \)

D

\(\frac{3}{5} \leq \frac{X}{Y} \leq \frac{8}{11} \)

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12

2013 · Life Sciences · Chemical Equilibria · Ionic Equilibria, Buffers and Solubility

Life Sciences (XL) 2013

When dissolved in water, the number of H⁺ ions released from a molecule of H₃BO₃ is ____________

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13

2013 · Life Sciences · Chemical Equilibria · Ionic Equilibria, Buffers and Solubility

Life Sciences (XL) 2013

The solubility product (\(K_{sp}\)) of Ca₃(PO₄)₂ is \(1.3 \times 10^{-32}\). In a 0.02 M solution of Ca(NO₃)₂, the solubility of Ca₃(PO₄)₂ (in units of M) is

A

\(6.5 \times 10^{-31}\)

B

\(1.6 \times 10^{-26}\)

C

\(8.0 \times 10^{-16}\)

D

\(4.0 \times 10^{-14}\)

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14

2013 · Life Sciences · Chemical Equilibria · Ionic Equilibria, Buffers and Solubility

Life Sciences (XL) 2013

You have prepared 1.0 liter of 0.5 M acetate buffer (pH=5.0). The dissociation constant of acetic acid is \(1.7\times10^{-5}\) M. What would be the acetate ion concentration in the buffer?

A

0.1 M

B

0.25 M

C

0.315 M

D

0.415 M

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15

2014 · Life Sciences · Chemical Equilibria · Ionic Equilibria, Buffers and Solubility

Life Sciences (XL) 2014

One litre of phosphate buffer was prepared by adding 208 grams of Na₂HPO₄ (Mol. wt. 142) and 71 grams of NaH₂PO₄ (Mol. wt. 120) in water. If the pK_a for the dissociation of H₂PO₄^- into HPO₄^2- and H⁺ is 6.86, the pH of the buffer will be ________.

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16

2018 · Life Sciences · Chemical Equilibria · Ionic Equilibria, Buffers and Solubility

Life Sciences (XL) 2018

The solubility product (Ksp) of Mg(OH)₂ at 25 °C is 5.6 × 10⁻¹¹. Its solubility in water is S × 10⁻² g/L, where the value of S is ______ (up to two decimal places). (Given: Molecular weight of Mg(OH)₂ = 58.3 g mol⁻¹)

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17

2018 · Life Sciences · Chemical Equilibria · Ionic Equilibria, Buffers and Solubility

Life Sciences (XL) 2018

Acid rain with a pH of 4.0 is more acidic than the rain with a pH of 6.0 by

A

2 times

B

10 times

C

100 times

D

1000 times

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18

2019 · Life Sciences · Chemical Equilibria · Ionic Equilibria, Buffers and Solubility

Life Sciences (XL) 2019

The pH of a 1.0 L buffer solution containing 0.2 mol of acetic acid (CH₃COOH) and 0.3 mol of sodium acetate (CH₃COONa) is 5.0. The Kₐ of acetic acid is P × 10⁻⁵, where the numerical value of P (rounded off to one decimal place) is ____

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19

2019 · Life Sciences · Chemical Equilibria · Ionic Equilibria, Buffers and Solubility

Life Sciences (XL) 2019

The electrostatic interaction energy between a positively charged atom A and negatively charged atom B separated by 3 Å in water is -6 kJ/mol. Considering the relative permittivity of water to be 80, the electrostatic interaction energy in kJ/mol (rounded off to one decimal place) between atoms A and B in vacuum is ______.

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20

2020 · Life Sciences · Chemical Equilibria · Ionic Equilibria, Buffers and Solubility

Life Sciences (XL) 2020

The second pKₐ of phosphoric acid is 6.8. The ratio of Na₂HPO₄ to NaH₂PO₄ required to obtain a buffer of pH 7.0 is ________ (rounded off to two decimal places).

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