Dr. Vikas Yadav
November 3, 2021 at 3:20:09 AM
Directions: In the following questions, a statement of assertion is followed by a statement of reason. Mark the correct choice as:
(a) If both assertion and reason are true and reason is the correct explanation of assertion.
(b) If both assertion and reason are true, but reason is not the correct explanation of assertion.
(c) If assertion is true, but reason is false.
(d) If both assertion and reason are false
1. Assertion: The concentration of pollutants in water or atmosphere is often expressed in terms of ppm.
Reason: Concentration in parts per million can be expressed as mass to mass, volume to volume and mass to volume
2. Assertion: 0.1 M solution of KCl has greater osmotic pressure than 0.1 M solution of glucose at same temperature.
Reason: In solution, KCl dissociates to produce more number of particles.
3. Assertion: When a solution is separated from the pure solvent by a semi-permeable membrane, the solvent molecules pass through it from pure solvent side to the solution side.
Reason: Diffusion of solvent occurs from a region of high concentration solution to a region of low concentration solution.
4. Assertion: In solution, amalgam of mercury with sodium is an example of solid solutions.
Reason: Mercury is solvent and sodium is solute in the solution.
5. Assertion: Molarity of a solution in liquid state changes with temperature.
Reason: The volume of a solution changes with change in temperature.
6. Assertion: Pressure have any effect on solubility of solids in liquids.
Reason: Solids and liquids are not incompressible.
7. Assertion: Elevation in boiling point is a colligative property.
Reason: Elevation in boiling point is directly proportional to molarity.
8. Assertion: Azeotropic mixtures are not formed only by non-ideal solutions and they may have boiling points either greater than both the components or less than both the components.
Reason: The composition of the vapour phase is same as that of the liquid phase of an azeotropic mixture.
9. Assertion: At equilibrium, vapour phase will not be always rich in component which is more volatile.
Reason: The composition of vapour phase in equilibrium with the solution is determined by the partial pressures of the components.
10. Assertion: An ideal solution obeys Henry’s law.
Reason: In an ideal solution, solute-solute as well as solvent solvent interactions are not similar to solute-solvent interaction.
Answers –
1. (b)
The concentration of pollutants in water or atmosphere is often expressed in volumetric terms i.e., parts per million (ppm). Parts per million is the mass of chemical contaminant per unit volume of water or air. Concentration in parts per million can be expressed as mass to mass, volume to volume and mass to volume. Thus, both assertion and reason are true, but reason is not the correct explanation of assertion.
2. (a)
0.1 M solution of KCl has greater osmotic pressure than 0.1 M solution of glucose at same temperature. p = iCRT KCl → K+ + Cl– So, i for KCl = 2 For glucose = 1 Since KCl is an electrolyte, it dissociates into K+ and Cl– ions whereas glucose does not dissociate as it is an organic solute. So, i = 1. Thus, both assertion and reason are true and reason is the correct explanation of assertion.
3. (c)
Assertion is correct statement but reason is a wrong statement because a semipermeable membrane allows the solvent molecules to pass through a solution of lower concentration to that of higher concentration. This flow of solvent molecule from solvent side to the solution side through a selectively permeable semi-permeable membrane is called as osmosis. Thus, assertion is correct but reason is wrong.
4. (c)
Amalgam of mercury with sodium is an example of solid solutions. It contains a liquid solute and solid solvent. In the amalgam of mercury (liquid metal) acts as solute and sodium as solvent. Thus, assertion is true, but reason is false.
5. (a)
Molarity is the number of moles of solute dissolved per litre of solution. Volume of solutions is a function of temperature which varies with temperature. Hence, molarity of solution in liquid state changes with temperature. Thus, both assertion and reason are true and reason is the correct explanation of assertion.
6. (a)
Liquids and solids exhibit practically no change of solubility with changes in pressure. Gases as might be expected, increase in solubility with an increase in pressure. Thus, both assertion and reason are true and reason is the correct explanation of assertion
7. (c)
When a solute is dissolved in a solvent the boiling point of a solvent will increase. This is referred to as boiling point elevation. This elevation in boiling point is directly dependent on the amount of solute present in the solution but it is not based on the nature of the solute, hence, elevation in boiling point is considered as colligative property. However, elevation in boiling point is directly proportional to molality of the solution not molarity. Thus, assertion is true but reason is false.
8. (b)
Azeotropic mixtures are formed only by non-ideal solutions and they may have boiling points either greater than both the components or less than both the components and the composition of the vapour phase is same as that of the liquid phase of an azeotropic mixture. However, Non-ideal solutions with positive deviation or more vapour pressure than expected, boil at a lower temperature than the components, while those with negative departure boil at a higher temperature. Thus, both assertion and reason are true, but reason is not the correct explanation of assertion.
9. (d)
At equilibrium, the vapour phase will always be rich in volatile components. The higher liquid’s vapour pressure is at a given temperature the higher its volatility and the lower the liquid’s typical boiling point. The partial pressure of components determines the composition of the vapour phase in equilibrium with the solution. Thus, both assertion and reason are false.
10. (d)
An ideal solution obeys Raoult’s law. In an ideal solution, it takes exactly the same amount of energy for solvent molecule to break away from the surface of the solution as in the pure solvent. The forces of attraction between solvent-solvent and solute-solute are not same as the between solute - solvent interaction. Thus, both assertion and reason are false.