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Long Answer Type

111. Define vapour pressure of a liquid. What happens to the vapour pressure of a liquid when (a) a volatile solute dissolves in it and (b) a non-volatile solute dissolves in it?

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Short Answer Type

112. What is osmotic pressure? How is it dependent on the number of moles of a solute?

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113. State Raoult’s law. If AT is the elevation of boiling point of a solvent and m is the number of moles of solute per kg of solvent, what is the realationship between T and m?

Raoult’s law: It states that whenever a non-volatile solute is added to a volatile solvent the vapour pressure of the solvent is lowered and the lowering of vapour pressure s directly proportional to the mole-fraction of the solute added.

p_A ∝ x_A

{P^{0}}_{A} - P_{A} = {P^{0}}_{A} X_{B}

\frac{{P^{0}}_{A} - P_{A}}{P_{A}^{0}} = X_{B}

where P⁰_A is the vapour pressure of the pure solvent.
P_A is the vapour pressure of the solution.
X_B is the mole fraction of non-volatile solute.
Thus, according to Raoult’s law, the relative lowering of vapour pressure is equal to the mole-fraction of the solute in solution.

247 Views

114.

(a) What are non-ideal solution?
(b) What role does the molecular interaction play in deciding the vapour pressure of solutions (i) alcohol and kerosene (ii) Chloroform and acetone.

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115. Why do colligative properties of an electrolyte solution of a given concentration are found to be larger than those of a non-electrolyte solution of the same concentration?

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116. Explain the following phenomena:
(i) Hemolysis
(ii) Crenation.

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117. Why do we observe abnormal molecular masses?

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118. How does osmotic pressure depend on molality of the solution?

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Long Answer Type

119. The molar mass of acetic acid determined from the measurement of a colligative property is greater than its formula molar mass. Explain why?

210 Views

Short Answer Type

120. Explain why solvent-solvent, solute-solute and solute-solvent interactions are important in determining the extent to which a solute dissolves in a solvent.

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