SYBSC Sem-II Chapter 2: Solutions PDF

## SYBSC Sem-II **Only for Bacicags** **Chapter 2: SOLUTIONS** ### Q1 Define solubility. Give unit. Describe factors affecting on it. * "The maximum amount of solute dissolved in 1 L of solution" * Its unit: g/L. * **Factors affecting:** * **Pressure:** If pressure increases solubility of gas...

## SYBSC Sem-II **Only for Bacicags** **Chapter 2: SOLUTIONS** ### Q1 Define solubility. Give unit. Describe factors affecting on it. * "The maximum amount of solute dissolved in 1 L of solution" * Its unit: g/L. * **Factors affecting:** * **Pressure:** If pressure increases solubility of gas in liquid increases & vice versa. * **Temperature:** As temperature increases, solubility is generally increased, except for exothermic and gaseous reactions. * **Nature of solute & solvent:** Polar/ionic solutes are easily soluble in polar solvents while non-polar/non-ionic solutes are easily soluble in non-polar solvents. ### Q2 Define following terms. 1. **Molarity:** "The number of moles of solute dissolved per liter of solution". * Unit: mol/L 2. **Molality:** "The number of moles of solute per 1000 gm of solvent". * Unit: mol/kg. 3. **Normality:** "The number of gm-equivalents of solute per liter of solution". * Unit: gm-equiv/L. 4. **Mole fraction:** "The number of moles of substance divided by the total number of moles in solution". * No **N_B** = No **N_A** + No **N_B** 5. **Vapour Pressure:** "The pressure created by vapours on the surface of liquid at a given temperature". ### Q3 State Raoult's Law: "The partial vapor pressure of any volatile component of a solution is equal to the vapor pressure of the pure component multiplied by the mole fraction of that component in the solution". * **P_A = N_A *P°_A** ### Q4 Mention characteristics of ideal & non-ideal solutions. * Describe ideal & non-ideal solutions. * Define ideal & non-ideal solutions. Give examples. #### Ideal Solution * Definition: Solution which obeys Raoult's Law * **ΔV_mix = 0** * **ΔH_mix =0** * Example: Benzene-toluene #### Non-ideal Solution * Definition: Solution which does not obey Raoult's law. * **ΔV_mix ≠ 0** * **ΔH_mix≠ o** * Example: Acetone -CS₂ ### Q5 Give the example of organic & inorganic semipermeable membrane. * **Organic:** 1. Cellulose in organic solvent. 2. Slice of potato. * **Inorganic:** 1. Cupric ferrocyanide on porous plate. ### Q6 Solve the following: 1. **Addition of non-volatile solute:** lowers the vapor pressure. 2. **Phenol-water system:** exhibits maximum CST. 3. **Molality of the solution:** is no. of moles of solute present in 1000 gm of solvent. 4. **Abnormal molecular weights:** are obtained when there exists either of two means dissociation or association. 5. **Molal elevation constant::** is elevation in boiling point when the molality of the solution is 1. 6. **The liquid mixture which shows maximum as well as minimum CST:** is Aniline-water. 7. **Which equation represents Raoult's law:** **P = P°_A (N_A + N_B)** 8. **Colligative properties:** are mainly dependent on the number of solute particles. ### Q7 Define critical solution temp. "The minimum (or maximum) temperature at which two partially miscible liquids become completely miscible is called". ### Q8 Define azeotrope. Give example. * Write note on azeotropes. * **Definition:** The minimum or maximum constant boiling liquid mixture which boils without change in its composition are called. * **Azeotropes acquire stability and fixed composition due to force of attraction between the molecules.** * **Examples:** * **Max B.P Azeotrope:** Water - ethanol (95-5%) * **Min B.P Azeotrope** Water - HNO3(68-5%) BP = 121 °C. * **Separation of Azeotropes by:** * Washing with solvent. * Distillation under high pressure ### Q9 Discuss the nicotine - Water System. * Explain partially miscible liquid pair has minimum critical solution temperature: **Temperature** * **Heterogeneous** * **Homogeneous** * **Heterogeneous** * **Homogeneous** * **Critical composition:** 30% Et₃N - 70% water. * **Critical Temperature:** 18.5 °C * **Curve AB:** for solubility of Et₃N in water. * **Curve BC:** for solubility of water in Et₃N. * **Area above ABC:** heterogeneous * **Area below ABC:** homogeneous ### Q10 Draw v.p. - concentration dig for ideal system (Hint p-x dig.) * What is p-x & T-x diagrams? * Discuss different types of P-x and T-x diagrams in case completely miscible liquids. #### P-x Digram * "The plot of vapor pressure verses composition is called." #### T-x Diagram * "The plot of temperature verses composition is called." **P-x diagrams** **Type-1- T = constant** * **Pure A (Cyclohexane)** * **Pure B (Carbon tetrachloride)** **Type-11- T = constant** * **Pure A (Methylal)** * **Pure B (Carbon disulfide)** **Type-111- T = constant** * **Pure A (Acetone)** * **Pure B (Chloroform)** **T-x diagrams** **Type-1- P =constant** * **Pure A** * **Pure B** **Type-11- P =constant** * **Pure A** * **Pure B** **Type-111- P =constant** * **Pure A** * **Pure B** ### P-x diagrams * **Type-1:** shows the deviation from Raoult's law. P_B° > P_A°. Liquid curve above while vapor curve is below. * **Type-II:** V.P. of liq. mixture C > P_B° > P_A°. Liq. mixture C shows max. one lobe pure A to C & second Pure B to C. * **Type-III:** V.P order is P°_B > P°_A > liq. mixture C. ### T-x diagrams * **Type-I:** Plot of B.P Vs mole fraction. T_A > T_B. Vapours are richer in more volatile liq. B while liquid residue are richer in less volatile liq.A. * **Type-II:** The liq. mixture C has minimum B.P & is called Azeotropes. The liq. mixture C has max. Critical solution temp. & partially miscible liquid pair has max. B.P. ### Q11 Define solubility. Discuss phenol - water system. * "Maximum amount of solute dissolved in 1 L of solution at a given temperature". Unit: gm⁄L. **Homogeneous** * **Critical composition:** 38-33% phenol * **Critical temperature:** 68.5 °C * **Heterogeneous** * **Area below ABC:** heterogeneous. * **Area above ABC:** homogeneous. * **Curve AB:** phenol in water * **Curve BC:** water in phenol ### Q12 Define fractional distillation. Explain construction and working of a fractionating column. * **Definition:** The process of separation of mixture carried out in a continuous manner using a fractionating column is called. **Construction and working** * **Fractionating column consists of:** * **Steel tank** and **column** * **Column** has horizontal plates with overflow tubes L₁, L₂… and bubble caps V₁, V₂…. * **Bottom** has liquid mixture and heating coil. * **Upper side** has condenser. **Working:** 1. The preheated liq. coming from a side tube. 2. Liquid mixture at the bottom boils. 3. Vapors enter through bubble caps to upward. 4. Liquid flow from overflow L₁ to L₂… soon. 5. The more volatile liquid goes upward to condenser 6. Less volatile liquid remains at the bottom. ### Q13 Write uses of a fractionating column. * Used in petroleum industry * Used in the laboratory to separate liquids. ### Q14 Define terms colloidal dispersion & true solution. * **Colloidal dispersion:** "The mixture formed by shaking fine particles in water". * Example: Fine clay in water. * **True solution (or solution):** "The homogeneous mixture of solute and solvent". ### Q15 Give different units (ways) to express concentration of solutions. * Molarity * Molality * Normality * % weight. ### Q16 State Dalton's law partial pressure. Write the composition of vapor of an ideal solution. * **Dalton's law:** "The partial vapor pressure of the component is the product of total vapor pressure and its mole fraction (Y_B)". * **P_B = Y_B P** * **Composition of vapor (Y_B)** is: * **Y_B = (N_B * P°_B)/( (P°_B - P°_A) * N_B + P°_A)** * Where: * **P°_A = V.P of pure liq. A** * **P°_B = V.P of pure liq. B** * **N_B = mole fraction of liq. B** ### Q17 Describe boiling-point-composition diagram of type-1/ type-II / type -III. * Write T-x diagrams page 2.5 & 2-6. ### Q18 State principle of fractional distillation. * **The two miscible liquids are separated in a continuous manner using a fractionating column by repeated distillations and condensations.** ### Q19 Describe the distillation diagrams of binary miscible solution of type-I. Draw distillation diagram of type I. * **T_A > T_B** * **Vapor compositions a', b' & c' richer in B** * **Liquid compositions a, b, & c richer in A** * **Vapor curve below & liquid curve above** * **B.P T_A liquid composition a & vapor composition a' which shifts toward B** ### Q20 Define activity of gas. * **Activity (a) = Partial pressure of gas/ pressure of pure gas** ### Q21 Describe distillation diagram of binary miscible solution of type - II. Draw type - II distillation diagram. * **B.P order: T_C > T_A > T_B C = liquid mixture.** * **Vapor compositions a' & b' richer in A** * **Vapor compositions c' & d' richer in B** * **Liquid compositions a, b, c & d richer in C** * **Liquid mixture C has maximum B.P & constant composition called azeotrope.** * **Vapor curve is above and liquid curve is below** ### Q22 Describe distillation diagram of binary miscible solution of type - III. * **B.P order: T_C > T_A > T_B C = liquid mixture.** * **Vapor compositions a' & b' richer in A** * **Vapor compositions c' & d' richer in B** * **Liquid compositions a, b, c & d richer in C** * **Liquid mixture C has maximum B.P & constant composition called azeotrope.** * **Vapor curve is above and liquid curve is below** **P = P_A N_A + P_B N_B** **= P_A N_A + P_B (1-N_A)** **76 = (82.72 * N_A) + 49.24 (1-N_A)** **76 = (82.75 - 49.24) * N_A + 49.24** **= (33.51) N_A + 49.24** **76 - 49.24** **N_A = ---------- =0.798** **33.51** **N_B = 1 - N_A = 1 - 0.798 = 0.202** **Y_B = (P°_B * N_B) / ( (P°_B- P°_A) * N_B + P°_A)** **= (49.20 * 0.202)/ ( (49.24- 82.75) * 0.202 + 82.75)** **= 9.946 / 75.981** **= **0.131** **Y_A = 1 - Y_B** **= 1 - 0.131 ** **= 0.869** ## Exercise **Multiple Choice Questions:** 1. In case of gases solubility **decreases** with increase in temperature. 2. In solid in liquid or liquid in liquid solubility is **decreases** with rise in temperature. 3. Moistener in water is an example of **liquid gas** solution. 4. Soda water is an example of **gas-liquid** solution. 5. A binary solution of cyclohexane and carbon tetrachloride is exhibited * **Both positive and negative deviation** from Raoult's law 6. The sum of mole fraction of solute and solvent is always **one**. 7. The system **Methylal and CS₂** shows negative deviation from Raoult's law 8. The ideal solution must satisfy the condition * **Activity is equal to molefraction** 9. The temperature at which vapour pressure of the liquid becomes equal to atmospheric pressure is more than one. 10. Which equation represents Raoult's law? * **P = P°_AN_A** 11. In fractionating column distillation of fraction is carried out by **Continuous Manner** 12. Distillation diagram are the plot of * **Vapour pressure verses Mole fraction of solvent** 13. The liquid mixture which boils without changes in its composition is called **Azeotropic mixture** 14. Phenol water system exhibits **minimum CST** system. 15. The liquid mixture which shows maximum as well as minimum critical solution temperature. * **Nicotin-water** 16. If n represents the number of a solute and N represents the number of moles of a solvent, the mole fraction of the solvent is given by **N⁄(n+N)** 17. The molarity is defined as the number of moles of solute present in **one litre of the solution** 18. The molality of a solution is defined as the number of moles of solute present in **one kilogram of the solvent** 19. Normality of a solution is the number of **equivalents** of solute per litre of solution. 20. The weight percent of a solute in solution is given by **(wt of the solute / wt of the solution) * 100** 21. The temperature at which two conjugate solutions (or layers) merge into one another to form one layer is called the **critical solution temperature** 22. The solubility generally rises with **decrease in pressure**. 24. The completely miscible solution can be separated by **evaporation** 25. In one molal solution that contains 0.5 mole of a solute there is **1000 g of solvent** 26. The number of moles of a solute per kilogram of the solvents is called **Molality** 27. A real solution is that which **does not obey Raoult's law** 28. According to Raoults' law the vapour pressure of a solution is related to **mole fraction of the solvent**. 29. An azeotropic solution of two liquids has a boiling point lower than either of them when it **shows positive deviation from Roult's law** 30. In a temperature composition curve of a mixture of two liquids, the presence of a maxima or minima indicates that **the liquids are partially soluble at the maximum or minimum** 31. Solutions which distil without change in composition or temperature are called **azeotropic mixture** 32. The partial miscibility of water and phenol is because of the fact that they **show positive deviation from Roult's law** 33. Very dilute solutions which show deviations (positive or negative) from Roult's law are called **Non- ideal solution** 34. How many types of solutions are possible by the combination of any two of the three states of matter (solid, liquid and gas) **9** 35. Molarity is expressed as **Moles/litre** 36. Molar concentration of a solution is **(No. of moles of solute/No. of litres of solution)** 37. The temperature at which the vapour pressure is equal to the external pressure is called the **Boiling point** 38. Azeotropic mixtures are **Constant boiling mixtures** 39. A mixture of two completely miscible non - ideal liquids which distil as such without change in its composition at a constant temperature as though it were a pure liquid. This mixture is known as **azeotropic mixture** 40. Identify the mixture that shows positive deviations from Raoult's law **CHCl3 + (CH3)2CO** 41. A mixture of benzene and toluene forms **non-ideal solution** 42. The solutions which show positive or negative deviation from Raoult's law are called **Non ideal solutions** 43. Which of the following liquid pairs shows a positive deviation from Roult's law? **Water - Hydrochloric acid** 44. Which of the following pairs shows a negative deviation from Raoult's law? **Acetone - Benzene** 45. If liquid A and B form an ideal solutions **the enthalpy of mixing is zero** 46. Units of mole fraction are **dimensionless** ## Questions 1. Define the term Molarity, Molality. 2. Define the term mole fraction with example. 3. Explain the term Mass fraction, Volume fraction. 4. Why the molarity of the solution changes with temperature. 5. Why does the molality remain unchanged with temperature? 6. Define the term solubility. 7. Define the term Vapour pressure. 8. Define and explain the term solution. 9. What are the different types of binary solution? 10. State Raoults law and state the factors responsible for the deviation from this law.