Solutions – Chapter 2 CBSE Class 12 Chemistry
Very Short Answer Questions
Q. 1. Define mole fraction. [CBSE Delhi 2012]
Ans. Mole fraction of a component in a solution may be defined as the ratio of moles of that component to the total number of moles of all the components present in the solution.
Q. 2. Why are the aquatic species more comfortable in cold water in comparison to warm water? [CBSE 2019 (56/2/3), (56/4/1)]
Ans. At a given pressure, the solubility of oxygen in water increases with decrease in temperature. Presence of more oxygen at lower temperature makes the aquatic species more comfortable in cold water.
Q. 3. What is the similarity between Raoult’s law and Henry’s law? [CBSE Delhi 2014]
Ans. The similarity between Raoult’s law and Henry’s law is that in both the laws, the partial vapour pressure of the volatile component or gas is directly proportional to its mole fraction in the solution.
Q. 4. Write two characteristics of non-ideal solution. [CBSE 2019 (56/5/2)]
Q. 5. Why is the vapour pressure of a solution of glucose in water lower than that of water? [NCERT Exemplar]
Ans. This is due to decrease in the escaping tendency of the water molecules from the surface of solution as some of the surface area is occupied by non-volatile solute, glucose particles.
Q. 6. What are isotonic solutions? [CBSE Delhi 2012, 2014]
Ans. The solutions of the same osmotic pressure at a given temperature are called isotonic solutions.
Q. 7. How is it that measurement of osmotic pressures is more widely used for determining molar masses of macromolecules than the elevation in boiling point or depression in freezing point of their solutions? [CBSE (AI) 2009]
Ans. The osmotic pressure method has the advantage over elevation in boiling point or depression in freezing point for determining molar masses of macromolecules because
- Osmotic pressure is measured at the room temperature and the molarity of solution is used instead of molality.
- Compared to other colligative properties, its magnitude is large even for very dilute solutions.
Q. 8. Out of two 0.1 molal aqueous solutions of glucose and of potassium chloride, which one will have a higher boiling point and why? [CBSE (F) 2013, 2019 (56/3/2)]
Ans. 0.1 m KCl solution will have higher boiling point as KCl dissociates in the solution.
Q. 9. Define an ideal solution. [CBSE OD 2013, 2012]
Ans. Solutions which obey Raoult’s law over the entire range of concentration at specific temperature.
Q. 10. Some liquids on mixing form ‘azeotropes’. What are ‘azeotropes’ ? [CBSE Delhi 2014]
Ans. Azeotropes : Binary mixtures having same composition in liquid and vapour phase and boil at a constant temperature.
Q. 11. What type of intermolecular attractive interaction exists in the pair of methanol and acetone ? [CBSE Delhi 2014]
Ans. Hydrogen bonding.