Class 12 CBSE Chemistry – Chapter 2: Solutions
Most Repeated Questions with Answers (Highlighted Points Included)
1. Q: State Henry's Law and write its two applications.
A: Henry’s Law: The solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid.
Applications:
- In soft drink bottles (more pressure = more gas dissolved).
- Deep-sea divers use special gas mixtures to avoid bends.
2. Q: Define mole fraction. What is the sum of mole fractions of all components in a solution?
A: Mole fraction (x) = moles of a component / total moles of all components.
Important: The sum of all mole fractions is always 1.
3. Q: State Raoult's Law for a solution containing volatile components.
A: Raoult's Law: The partial vapor pressure of each component is proportional to its mole fraction in the solution.
pA = xA × pA°, where xA = mole fraction, pA° = pure vapor pressure.
4. Q: What is the effect of temperature on solubility of a solid in a liquid?
A: Solubility increases with temperature if dissolution is endothermic. If exothermic, solubility decreases.
5. Q: Why is the vapor pressure of a solution lower than that of a pure solvent?
A: Because some solvent molecules are replaced by solute, reducing the number of molecules escaping as vapor.
6. Q: What happens when external pressure is applied to a gas above the liquid?
A: According to Henry’s Law, gas solubility increases with pressure.
7. Q: Write the mathematical expression for Henry’s law.
A: p = kH × x
8. Q: Explain the term 'ideal solution' with one example.
A: An ideal solution obeys Raoult’s law at all compositions and temperatures. Example: n-hexane + n-heptane
9. Q: What is the significance of i (van’t Hoff factor) in colligative properties?
Most Repeated Questions with Answers (Highlighted Points Included)
1. Q: State Henry's Law and write its two applications.
A: Henry’s Law: The solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid.
Applications:
- In soft drink bottles (more pressure = more gas dissolved).
- Deep-sea divers use special gas mixtures to avoid bends.
2. Q: Define mole fraction. What is the sum of mole fractions of all components in a solution?
A: Mole fraction (x) = moles of a component / total moles of all components.
Important: The sum of all mole fractions is always 1.
3. Q: State Raoult's Law for a solution containing volatile components.
A: Raoult's Law: The partial vapor pressure of each component is proportional to its mole fraction in the solution.
pA = xA × pA°, where xA = mole fraction, pA° = pure vapor pressure.
4. Q: What is the effect of temperature on solubility of a solid in a liquid?
A: Solubility increases with temperature if dissolution is endothermic. If exothermic, solubility decreases.
5. Q: Why is the vapor pressure of a solution lower than that of a pure solvent?
A: Because some solvent molecules are replaced by solute, reducing the number of molecules escaping as vapor.
6. Q: What happens when external pressure is applied to a gas above the liquid?
A: According to Henry’s Law, gas solubility increases with pressure.
7. Q: Write the mathematical expression for Henry’s law.
A: p = kH × x
8. Q: Explain the term 'ideal solution' with one example.
A: An ideal solution obeys Raoult’s law at all compositions and temperatures. Example: n-hexane + n-heptane
9. Q: What is the significance of i (van’t Hoff factor) in colligative properties?
