Solutions - Subjective questions on Solubility of solids in liquids

 

                                                                 Subjective Questions

1. Why is benzene soluble in toluene but not in water?

Sol.  “Like dissolves like”. Benzene and toluene are non-polar; H₂O is polar.

2. Explain, why solute-solute, solvent-solvent and solute-solvent interactions are important in determining the extent to which a solute dissolves in a solvent?

Sol: In the dissolution process, solute – solute, solvent – solvent interaction overcome and solute – solvent interactions are overcome and solute – solvent interactions are established. The solubility of a solute thus, depends on the strength of new solute – solvent interactions relative to the strengths of solute – solute and solvent – solvent interactions.

3. Indicate the type of solute – solvent inter molecular forces that should be most important in each of the following solutions:

(a) KCl in water (b) C₆H₆ in CCl₄ (c) HF in water

(d) CH₃OH in water (e) C₆H₆ in cyclohexane (f) HCl in CH₃CN

Sol: (a) Ion – dipole (b) London dispersion (c) H – bonding

(d) H – bonding (e) London dispersion (f) dipole - dipole

4.  Suppose a solid solution is formed between two substances, one whose particles are very large and other whose particles are very small. What type of solid solution is this likely to be?

Sol. Since, one substance has particles of very small size compared to the other, it will occupy the interstitial places in the host lattice of larger particles. So it is an interstitial solid solution.

5.  Why are some solution processes exothermic whereas others are endothermic?

Sol. The overall energy change associated with dissolution depends on the relative magnitude of the solute – solute, solvent – solvent and solute – solvent interactions. The process is exothermic if the new interaction releases more energy than disrupting the old interactions requires, it is endothermic if the opposite is true.