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Equilibrium

Short Answer Type

291.

Calculate the degree of hydrolysis of 0.015 M solution of NH₄Cl. Given K_b for NH₄OH is 1·8 × 10^–5, K_w = 10^–14at 25°C.

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Long Answer Type

292.

Explain the terms: buffer solution and buffer capacity.

200 Views

293.

Show with an example how buffer solution resists the action of acid or base towards change in pH.
Or
Discuss the buffer action of:
(i) acidic buffer
(ii) basic buffer.

133 Views

294. How will you explain buffer action of aqueous solution of ammonium acetate?

Ammonium acetate on dissolution dissociates completely as ions.

(i) If an acid (say HCl) is added to this solution, H₃O⁺ ions generated by the acid combine with CH₃COO^– ion to form weakly ionised acetic acid molecules

Since most of H₃O⁺ ions are consumed by CH₃COO^– ions to form slightly dissociated acetic acid, hence the pH value of the solution does not undergo any change.

Now suppose a base (say NaOH) is added to ammonium acetate solution. The OH^– ions liberated by the base will be consumed by

ions to form very slightly dissociated NH₄OH.

Since most of the OH^– ions are consumed by the

ions, hence there is very little or no change in the pH value of ammonium acetate.
Thus, CH₃COONH₄ has reserve acidity due to

ions and reserve alkalinity due to CH₃COO^– ions.

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295.

Calculate the pH of:
(i) an acidic buffer mixture
(ii) a basic buffer mixture.
Or
Derive Henderson’s equation for an acidic and basic buffer mixture.
Or
Derive the following equation for the pH of an acidic buffer:
$pH space equals space pK subscript straight a space plus space log space fraction numerator open vertical bar Salt close vertical bar over denominator open vertical bar Acid close vertical bar end fraction$

662 Views

Short Answer Type

296. Calculate the pH value of a solution obtained by mixing 0·083 moles of acetic acid and 0·091 moles of sodium acetate and making the volume 500 ml. K_a for acetic acid is 1·75 × 10^–5.

120 Views

Long Answer Type

297. Calculate the pH of a solution obtained by mixing 6·0g of acetic acid and 12·30g of sodium acetate and making the volume of solution to 500 ml. K_a for acetic acid is 1·8 × 10^–5

122 Views

298. Determine the pH of a solution obtained by mixing equal volumes of 0·015N NH₄OH and 0·15N NH₄NO₃ solutions. (K_b for NH₄OH is 1·8 × 10^–5).

127 Views

299.

Describe Ostwald’s theory of acid-base indicators.
Or
How does Ostwald’s theory explain the colour change of:
(i) Phenolphthalein
(ii) Methyl orange in acid-base titrations?

513 Views

Short Answer Type

300.

How does the concept of solubility product help in finding out the solubility of sparingly soluble salts?

142 Views