Chem Notes 1st Year Chap 4
Important Questions
Q In the hydrogen bonded structure of HF which is stronger bond. The shorter covalent or the longer Hydrogen bond between the different molecules.
Ans: Hydrogen bond of HF is shown below
Shorter covalent bond H___F is stronger than the longer Hydrogen bond F.....,H longer bond. The Covalent bond is twenty times Stronger than the hydrogen.
Q In a very cold water fish in garden ponds owe their lives to H-bonding.
Ans: When the temperature surroundings falls up to 4 C Degree water on the surface is freezes. During the process of freezing water molecule arrange in hexagonal fashion due to the hydrogen bonding and empty spaces are created. As a result volume of ice increases and density decreases. This layer of ice insulates the water under it for further heat loss which stays at 4 C degree as liquid. Hence fish can survive at this temperature and all this is due to the hydrogen bonding.
Q Water and ethanol can mix easily and in all proportions.
Ans: Ethyl alcohol and water can mix easily into each other in all proportions because both of hydrogen bonding with each other..
Q Sodium is softer than copper but both are good electrical conductors.
Ans: Strength of metallic bond depends upon the number of delocalized electron and the metallic radius. Greater number of delocalized electron and smaller the metallic radius stronger the metallic bond.
In case of copper the number of delocalized electron is larger than the sodium and also the metallic radius of sodium is more than that of copper so sodium is softer than the copper. But both are good conductor of Electricity due to availability of free electrons.
Q Diamond is hard and an electrical insulators.
Ans: In the diamond the carbon atoms are bonded with each other in three dimensional structure tetrahedral fashion which is the most stable structure resulting in the hardest naturally occurring substance. Since all the four valance electrons are involved in bond formation with neighbouring carbons therefore no free electron is available hence diamond is an insulator.
Q Sodium chloride and cesium chloride have different structure.
Ans: In the ionic compounds the structure depends upon the co ordination number of the metal. Sodium chloride and cesium chloride has different structure as the atom of sodium being smaller in size has the co ordination number of six whereas the Cesium being larger in size has the co ordination number eight so they posses different structures.
NaCl has the face centered cubic structure
CsCl has body centered cubic structure.
Q Iodine dissolves readily in tetra chloro methane or carbon tetra chloride.
Ans: Iodine is more soluble in carbon tetra chloride because both are non pollar in nature. Iodine is 85 times more soluble in carbon tetra chloride than in water.
Q Vapour pressure of solids are far less than those of liquids.
Ans: Vapour pressure of a substance depends upon the strength of intermolecular forces, greater the intermolecular forces less will be the vapour pressure of that substance. In case of solid there exist strong inter molecular forces as compared to that of liquids therefore, the vapour pressure of the solid is far less as compared the liquids.
Q Amorphus solid like glass is also called super coled liquids.
Ans: The temperature of many liquids may be lowered below their freezing point before crystallization statrs. A liquid existing at a temperature below its freezing point is called super cooled liquid. It has metastable condition. It is not in equilibrium with the solid.
Q Cleavage of the crystals is it self anisotropic behaviour.
Ans: the properties that differ in different directions trough crystalline solid are called anistropic properties. Cleavage is the breakage of crystal along the definite direction or planes. Since cleavage takes place only in particular directions so it exhibits anisotopic behaviour.
Q In the hydrogen bonded structure of HF which is stronger bond. The shorter covalent or the longer Hydrogen bond between the different molecules.
Ans: Hydrogen bond of HF is shown below
Shorter covalent bond H___F is stronger than the longer Hydrogen bond F.....,H longer bond. The Covalent bond is twenty times Stronger than the hydrogen.
Q In a very cold water fish in garden ponds owe their lives to H-bonding.
Ans: When the temperature surroundings falls up to 4 C Degree water on the surface is freezes. During the process of freezing water molecule arrange in hexagonal fashion due to the hydrogen bonding and empty spaces are created. As a result volume of ice increases and density decreases. This layer of ice insulates the water under it for further heat loss which stays at 4 C degree as liquid. Hence fish can survive at this temperature and all this is due to the hydrogen bonding.
Q Water and ethanol can mix easily and in all proportions.
Ans: Ethyl alcohol and water can mix easily into each other in all proportions because both of hydrogen bonding with each other..
Q Sodium is softer than copper but both are good electrical conductors.
Ans: Strength of metallic bond depends upon the number of delocalized electron and the metallic radius. Greater number of delocalized electron and smaller the metallic radius stronger the metallic bond.
In case of copper the number of delocalized electron is larger than the sodium and also the metallic radius of sodium is more than that of copper so sodium is softer than the copper. But both are good conductor of Electricity due to availability of free electrons.
Q Diamond is hard and an electrical insulators.
Ans: In the diamond the carbon atoms are bonded with each other in three dimensional structure tetrahedral fashion which is the most stable structure resulting in the hardest naturally occurring substance. Since all the four valance electrons are involved in bond formation with neighbouring carbons therefore no free electron is available hence diamond is an insulator.
Q Sodium chloride and cesium chloride have different structure.
Ans: In the ionic compounds the structure depends upon the co ordination number of the metal. Sodium chloride and cesium chloride has different structure as the atom of sodium being smaller in size has the co ordination number of six whereas the Cesium being larger in size has the co ordination number eight so they posses different structures.
NaCl has the face centered cubic structure
CsCl has body centered cubic structure.
Q Iodine dissolves readily in tetra chloro methane or carbon tetra chloride.
Ans: Iodine is more soluble in carbon tetra chloride because both are non pollar in nature. Iodine is 85 times more soluble in carbon tetra chloride than in water.
Q Vapour pressure of solids are far less than those of liquids.
Ans: Vapour pressure of a substance depends upon the strength of intermolecular forces, greater the intermolecular forces less will be the vapour pressure of that substance. In case of solid there exist strong inter molecular forces as compared to that of liquids therefore, the vapour pressure of the solid is far less as compared the liquids.
Q Amorphus solid like glass is also called super coled liquids.
Ans: The temperature of many liquids may be lowered below their freezing point before crystallization statrs. A liquid existing at a temperature below its freezing point is called super cooled liquid. It has metastable condition. It is not in equilibrium with the solid.
Q Cleavage of the crystals is it self anisotropic behaviour.
Ans: the properties that differ in different directions trough crystalline solid are called anistropic properties. Cleavage is the breakage of crystal along the definite direction or planes. Since cleavage takes place only in particular directions so it exhibits anisotopic behaviour.
Thank you so much very helpful and simple notes love u man
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