Physical Chemistry Master Series
Solutions Master Q&A
Strictly compiled 100 Questions and Answers for Class 12 covering Classification, Henry & Raoult's Laws, Azeotropes, and Colligative Properties.
100 Short Q&A Facts
- Q1: What is a solution?A: A solution is a homogeneous mixture of two or more substances.
- Q2: What is a solute?A: The substance that is dissolved in a solution is called the solute.
- Q3: What is a solvent?A: The substance that dissolves the solute is called the solvent.
- Q4: Give an example of a solid in liquid solution.A: Salt in water.
- Q5: Give an example of a gas in liquid solution.A: Carbon dioxide in soda water.
- Q6: What is a liquid in liquid solution?A: Alcohol in water is an example.
- Q7: Name a gas in gas solution.A: Air (oxygen in nitrogen).
- Q8: What is a solid in solid solution?A: Alloys like brass (zinc in copper).
- Q9: How are solutions classified based on physical state?A: Into solid, liquid, and gaseous solutions.
- Q10: What are dilute solutions?A: Solutions with a small amount of solute.
- Q11: What are concentrated solutions?A: Solutions with a large amount of solute.
- Q12: What is a saturated solution?A: A solution in which no more solute can dissolve at a given temperature.
- Q13: What is an unsaturated solution?A: A solution that can dissolve more solute at the same temperature.
- Q14: What is a supersaturated solution?A: A solution that contains more solute than it can hold at that temperature.
- Q15: What is meant by the concentration of a solution?A: The amount of solute present in a given quantity of solvent or solution.
- Q16: How can you express concentration?A: In terms of percentage, molarity, molality, and normality.
- Q17: What is molarity?A: Moles of solute per litre of solution.
- Q18: What is molality?A: Moles of solute per kg of solvent.
- Q19: What is normality?A: Gram equivalents of solute per litre of solution.
- Q20: What is mass percentage?A: (Mass of solute / Mass of solution) $\times$ 100.
- Q21: What is volume percentage?A: (Volume of solute / Volume of solution) $\times$ 100.
- Q22: What is mole fraction?A: Ratio of moles of one component to total moles of all components.
- Q23: What affects the solubility of a solute?A: Temperature, pressure, and nature of solute and solvent.
- Q24: How does temperature affect solubility?A: For most solids, solubility increases with temperature.
- Q25: How does pressure affect solubility of gases?A: Solubility of gases increases with pressure (Henry's law).
- Q26: What is Henry's Law?A: It states that the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid.
- Q27: Give the mathematical expression of Henry's Law.A: $C = kP$, where C is solubility, k is Henry’s constant, and P is pressure.
- Q28: What does Henry's constant (k) signify?A: It indicates the solubility of a gas at a particular pressure.
- Q29: How does temperature affect Henry's constant?A: Henry’s constant increases with temperature, meaning gas solubility decreases.
- Q30: Name a real-life application of Henry’s Law.A: Carbonated beverages are bottled under high pressure to increase $CO_2$ solubility.
- Q31: How is Henry’s Law used in scuba diving?A: It helps explain nitrogen narcosis; high pressure causes more nitrogen to dissolve in the blood.
- Q32: What happens to gases at high altitudes based on Henry’s Law?A: Lower pressure causes gases like oxygen to dissolve less in blood, leading to altitude sickness.
- Q33: How does Henry's Law relate to respiration in humans?A: It explains the exchange of oxygen and carbon dioxide in the lungs based on partial pressures.
- Q34: What is Raoult's Law?A: It states that the partial vapor pressure of a component in a solution is directly proportional to its mole fraction.
- Q35: Give the formula for Raoult's Law.A: $P_1 = X_1P_1^0$, where $P_1$ is the partial vapor pressure, $X_1$ is mole fraction, and $P_1^0$ is vapor pressure of pure solvent.
- Q36: What is total vapor pressure of a solution?A: It is the sum of partial vapor pressures of all components.
- Q37: How is total vapor pressure calculated in a binary solution?A: $P_{total} = X_1P_1^0 + X_2P_2^0$.
- Q38: What is Dalton’s Law of Partial Pressures?A: The total pressure exerted by a mixture of gases is the sum of the partial pressures.
- Q39: How is Raoult's law related to Dalton’s law?A: Raoult's law provides partial pressures in liquid mixtures, which can be summed using Dalton’s law.
- Q40: What is relative lowering of vapor pressure?A: It is the decrease in vapor pressure when a non-volatile solute is added to a solvent.
- Q41: How does Raoult’s Law help determine molar mass?A: By measuring vapor pressure lowering, molar mass of a solute can be calculated.
- Q42: What is the effect of a non-volatile solute on vapor pressure?A: It lowers the vapor pressure of the solvent.
- Q43: How is Raoult’s law important in colligative properties?A: It explains phenomena like boiling point elevation and freezing point depression.
- Q44: What is an ideal solution?A: A solution that obeys Raoult’s law over the entire composition range.
- Q45: What are the characteristics of an ideal solution?A: No enthalpy change ($\Delta H_{mix} = 0$) and no volume change ($\Delta V_{mix} = 0$) on mixing.
- Q46: Give an example of an ideal solution.A: Benzene and toluene.
- Q47: What is a non-ideal solution?A: A solution that does not obey Raoult’s law over the entire composition range.
- Q48: What are the types of non-ideal solutions?A: Positive deviation and negative deviation from Raoult’s law.
- Q49: What is positive deviation from Raoult's Law?A: When the total vapor pressure is more than expected due to weaker intermolecular forces.
- Q50: Give an example of a solution showing positive deviation.A: Ethanol and acetone.
- Q51: What is negative deviation from Raoult's Law?A: When the total vapor pressure is less than expected due to stronger intermolecular forces.
- Q52: Give an example of a solution showing negative deviation.A: Chloroform and acetone.
- Q53: What causes deviation in non-ideal solutions?A: Different strength of intermolecular forces between solute and solvent.
- Q54: What is an azeotrope?A: A constant boiling mixture of two or more liquids that behaves like a single substance.
- Q55: Why are azeotropes called constant boiling mixtures?A: Because they boil at a constant temperature without change in composition.
- Q56: What are the types of azeotropes?A: Minimum boiling azeotropes and maximum boiling azeotropes.
- Q57: What is a minimum boiling azeotrope?A: A mixture that boils at a lower temperature than either component.
- Q58: Give an example of a minimum boiling azeotrope.A: Ethanol and water (95% ethanol).
- Q59: What is a maximum boiling azeotrope?A: A mixture that boils at a higher temperature than either component.
- Q60: Give an example of a maximum boiling azeotrope.A: Hydrochloric acid and water (20% HCl).
- Q61: Why can't azeotropes be separated by simple distillation?A: Because they vaporize without change in composition.
- Q62: How are azeotropes separated?A: Using special techniques like azeotropic distillation or adding a third component.
- Q63: How does Raoult’s law explain azeotrope formation?A: Azeotropes form due to large deviations from Raoult’s law.
- Q64: What is the composition of an azeotrope dependent on?A: It depends on the nature of the components and temperature.
- Q65: Are azeotropes ideal or non-ideal solutions?A: They are non-ideal solutions.
- Q66: What is meant by constant composition distillation?A: Distillation where the vapor and liquid phases have the same composition, as in azeotropes.
- Q67: Can azeotropes be binary or ternary?A: Yes, they can be made up of two (binary) or more (ternary) components.
- Q68: Why are azeotropes important in industry?A: They affect the purity and separation of chemicals in industrial distillation processes.
- Q69: What are colligative properties?A: Properties that depend on the number of solute particles and not on their nature.
- Q70: Name the four main colligative properties.A: Relative lowering of vapor pressure, elevation of boiling point, depression of freezing point, and osmotic pressure.
- Q71: What is relative lowering of vapor pressure?A: The decrease in vapor pressure of a solvent due to the addition of a non-volatile solute.
- Q72: Write the formula for relative lowering of vapor pressure.A: $(P_0 - P) / P_0 = n_2 / (n_1 + n_2)$, where $P_0$ = vapor pressure of pure solvent, $P$ = solution, $n_1$ = moles of solvent, $n_2$ = moles of solute.
- Q73: What is elevation of boiling point?A: The increase in boiling point of a solvent when a non-volatile solute is added.
- Q74: What is the formula for elevation of boiling point?A: $\Delta T_b = K_b \times m$, where $K_b$ is the ebullioscopic constant and $m$ is molality.
- Q75: What is depression of freezing point?A: The decrease in freezing point of a solvent due to a non-volatile solute.
- Q76: What is the formula for depression of freezing point?A: $\Delta T_f = K_f \times m$, where $K_f$ is the cryoscopic constant and $m$ is molality.
- Q77: What is osmotic pressure?A: The pressure required to stop the flow of solvent into a solution through a semipermeable membrane.
- Q78: What is the formula for osmotic pressure?A: $\Pi = CRT$, where C = concentration, R = gas constant, T = temperature.
- Q79: What is a semipermeable membrane?A: A membrane that allows only solvent molecules to pass through, not solute particles.
- Q80: What is osmosis?A: The movement of solvent molecules through a semipermeable membrane from a dilute to a concentrated solution.
- Q81: What is reverse osmosis?A: Forcing solvent through a semipermeable membrane from concentrated to dilute side by applying pressure greater than osmotic pressure.
- Q82: How is molar mass determined using colligative properties?A: By measuring the extent of a colligative property like $\Delta T_f$, $\Delta T_b$, $\Pi$, or vapor pressure lowering.
- Q83: What is the van’t Hoff factor (i)?A: The ratio of actual number of particles in solution after dissociation or association to the number of formula units initially dissolved.
- Q84: Write the formula for van’t Hoff factor.A: $i = \text{Normal colligative property} / \text{Observed colligative property}$.
- Q85: What is the effect of dissociation on colligative properties?A: It increases the number of particles, thus increasing the effect.
- Q86: What is the effect of association on colligative properties?A: It decreases the number of particles, thus decreasing the effect.
- Q87: What kind of solutes affect colligative properties?A: Only non-volatile solutes affect colligative properties.
- Q88: Why are colligative properties called colligative?A: Because they depend on the “collection” or number of solute particles.
- Q89: How does ionic solute affect colligative properties?A: Ionic solutes dissociate into multiple particles, increasing the colligative effect.
- Q90: Give an example where colligative property helps in real life.A: Adding salt to icy roads lowers the freezing point of water.
- Q91: Which property is used in determining the molar mass of proteins?A: Osmotic pressure.
- Q92: Why is osmotic pressure preferred for molar mass of biomolecules?A: Because it can be measured accurately even at low concentrations.
- Q93: What is abnormal molar mass?A: Molar mass determined from colligative properties that deviates due to association or dissociation of solute particles.
- Q94: If a solute associates in solution (like acetic acid in benzene), what is the value of 'i'?A: $i < 1$.
- Q95: If a solute dissociates completely (like NaCl in water), what is the value of 'i'?A: $i = 2$ (since it forms $Na^+$ and $Cl^-$).
- Q96: What is an isotonic solution?A: Two solutions having the same osmotic pressure at a given temperature.
- Q97: What happens to a red blood cell placed in a hypertonic solution?A: It shrinks (plasmolysis) as water flows out due to osmosis.
- Q98: What happens to a red blood cell placed in a hypotonic solution?A: It swells and may burst as water flows in.
- Q99: What is the condition for using the formula $\Pi = CRT$?A: The solution must be dilute.
- Q100: Why is the freezing point depression constant ($K_f$) dependent only on the solvent?A: Because it is an intrinsic property of the pure solvent derived from its enthalpy of fusion and freezing point.
Part 1: Solutions and Their Classification
Part 2: Henry's Law and Raoult's Law
Part 3: Ideal & Non-Ideal Solutions, Azeotropes
Part 4: Colligative Properties
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