11th Chemistry Chapter 4 Notes

• Describe various types of intermolecular forces.
• Define intramolecular forces.
• What are dipole-dipole forces? Give an example.
• What are dipole-induced dipole forces or Debye forces?
• What are instantaneous dipole-induced dipole forces or London dispersion forces? 
• Why the boiling point of halogens increase down the group?
• Show hydrogen bonding between acetone and chloroform.
• The hydrides of group IV-A have low boiling points as compared to hydrides of group V-A, VI-A and VII-A. Justify.
• Why water is liquid but H2S and H2Se are gases?
• Why HF has lower boiling point than H2O?
• Ice occupies more space than water. Give reason.
• Why fish survive in winter in frozen ponds?
• How the size of electronic cloud affects London forces?
• Define liquid crystals. Give an example.
• Mention the biological applications of liquid crystals.
• What are unit cell dimensions or crystallographic elements? 
• How the cleansing action of soaps and detergents is due to hydrogen bonding?
• Lower alcohols are water soluble but corresponding alkanes are insoluble in water.  
• Why intramolecular forces are stronger than intermolecular forces?
• Lower alcohols are soluble into water but hydrocarbons are not. Give reason. 
• Write a brief note on solubility of hydrogen bonded molecules.
• Earthen ware vessels keep water cool. Explain.
• Explain why evaporation takes place at all temperatures?
• Why boiling point of water is different at Murree Hills and at Mount Everest?
• Why different liquids evaporate at different rates even at the same temperature? 
• Vacuum distillation can be used to avoid decomposition of sensitive liquids. Explain.
• Why heat of sublimation of iodine is very high? 
• Cleavage is an anisotropic behaviour. Explain it. 
• How the liquid crystals help in the detection of blockages in veins and arteries. OR How are liquid crystals used to locate veins, arteries, infections and tumors?
• What is relationship between polymorphism and allotropy?  
• Transition temperature is the term used for elements as well as compounds. Explain.
• The vapor pressure of diethyl ether is higher than water at same temperature?
• Describe that heat of sublimation is greater than heat of vaporization.
• Why the electrical conductivity of metals decrease by increasing temperature?
• What is meant by dynamic equilibrium? Give an example
• HF is weaker acid than HCl. Why?
• In the hydrogen bonded structure of HF, which is stronger bond? The shorter covalent bond or the longer hydrogen bond between different molecules.
• In a very cold winter the fish in garden ponds owe their lives to hydrogen bonding? 
• Dynamic equilibrium is established during evaporation of liquid in a closed vessel at constant temperature.
• Crystals of salts fracture easily, but metals are deformed under stress without fracturing. Explain the difference. 
• What is the difference between cubic close packing and hexagonal close packing?
• Explain cubic, tetragonal, orthorhombic, monoclinic, hexagonal, rhombohedral and triclinic system.
• Name the method used to determine vapour pressure. Mention the mathematical expression applied.
• Tell about hydrogen bonding in DNA helical structure and proteins.
• Why do Metals have Metallic Luster? 
•  Ionic crystals don’t conduct electricity in the solid state. Justify.
• In the closest packing of atoms of metals, only 74% space is occupied. Justify. 
• The number of positive ions surrounding the negative ions in the ionic crystal lattice depends upon the sizes of the two ions. 
• Amorphous solid like glass is also called super cooled liquid. Justify.
• Sodium chloride and Caesium chloride have different structures. Justify.
• The vapour pressures of solids are far less than those of liquids. Justify. 
• Sodium is softer than copper, but both are very good electrical conductors. Justify.