The enthalpy of transition of crustalline boron to amorphous boron at `1500^(@)C` is 0.4 kcal "mole"^(-1)`. Assuming at.wt of boron 10, the change in enthaplpy of transition 50 g boron from crystalline to amorphous form is

Heat of reaction is the change in enthalpy or internal energy as represented by a balanced thermochemical equation . The amount of energy released during a chemical change depends upon the state of reactants and products, the conditions of pressure and volume at which reaction is carried out, and temperature. The variation of heat of reaction (DeltaH_(1) or DeltaE) with temperature is given as DeltaH_(2)-DeltaH_(1)=DeltaC_(P)[T_(2)-T_(1)] or DeltaE_(2)-DeltaE_(1)=DeltaC_(v)(T_(2)-T_(1). Standard heat enthalpy of elements in their most stable state is assumed to be zero whereas standard heat enthalpy of compound is referred as heat of formation of that compound at 1 atm pressure and 25^(@)C . Oxidation of N_(2) to N_(2)O,NO,NO_(2) shows absorption of energy whereas heat of combustion of N_(2) is exothermic like other heat of combustion. Heat of combustion of carbon in diamond and amorphous form ar -94.3 and -97.6 kcal//mol . The heat required to convert 6g carbon from diamond to amorphous form is :

Borane is an electron deficient compound. It has only six valence eletons, so the boron atom lacks an octet. Acquiring an octet is the driving force for the unusual bonding structure found in boron compounds. As an electron deficient compound, BH_(3) is a strong electrophile, capable of adding to a double bond. This hydroboration of double bond is though to oC Cur in one step, with the boron atom adding to the less highly substituted end of the double bond. In transition state, the boron atom withdraws electrons from the pi bond and the carbon at theother end of the double bond acquires a partial positive charge. This positive charge is more stable on the more highly subsituted carbon atom. The second step is the oxidation of boron atom, removing it from carbon and replacing it with hydroxyl group by using H_(2)O_(2)//OH^(bar(..)) . The simultaneous addition of boron and hydrogen to the double bond leads to a syn addition. Oxidation of the trialkyl borane replaces boron with a hydroxyl group in the same stereochemical position. Thus, hydroboration of alkenen is an example of steropecific reaction, in which different steroisomers of starting compounds react to give different steroisomers of the product. CH_(3)-underset(CH_(3))underset(|)overset(CH_(3))overset(|)C-CH=CH_(2) underset((ii)H_(2)O_(2)//OH^(bar(..)))overset((i)BH_(3)//THF)rarrZ . Z is :

Borane is an electron deficient compound. It has only six valence eletons, so the boron atom lacks an octet. Acquiring an octet is the driving force for the unusual bonding structure found in boron compounds. As an electron deficient compound, BH_(3) is a strong electrophile, capable of adding to a double bond. This hydroboration of double bond is though to oC Cur in one step, with the boron atom adding to the less highly substituted end of the double bond. In transition state, the boron atom withdraws electrons from the pi bond and the carbon at theother end of the double bond acquires a partial positive charge. This positive charge is more stable on the more highly subsituted carbon atom. The second step is the oxidation of boron atom, removing it from carbon and replacing it with hydroxyl group by using H_(2)O_(2)//OH^(bar(..)) . The simultaneous addition of boron and hydrogen to the double bond leads to a syn addition. Oxidation of the trialkyl borane replaces boron with a hydroxyl group in the same stereochemical position. Thus, hydroboration of alkenen is an example of steropecific reaction, in which different steroisomers of starting compounds react to give different steroisomers of the product. CH_(3)-underset(CH_(3))underset(|)overset(CH_(3))overset(|)C-CH=CH_(2) underset((ii)H_(2)O_(2)//OH^(bar(..)))overset((i)BH_(3)//THF)rarrZ . Z is :

Borane is an electron deficient compound. It has only six valence eletons, so the boron atom lacks an octet. Acquiring an octet is the driving force for the unusual bonding structure found in boron compounds. As an electron deficient compound, BH_(3) is a strong electrophile, capable of adding to a double bond. This hydroboration of double bond is though to oC Cur in one step, with the boron atom adding to the less highly substituted end of the double bond. In transition state, the boron atom withdraws electrons from the pi bond and the carbon at theother end of the double bond acquires a partial positive charge. This positive charge is more stable on the more highly subsituted carbon atom. The second step is the oxidation of boron atom, removing it from carbon and replacing it with hydroxyl group by using H_(2)O_(2)//OH^(bar(..)) . The simultaneous addition of boron and hydrogen to the double bond leads to a syn addition. Oxidation of the trialkyl borane replaces boron with a hydroxyl group in the same stereochemical position. Thus, hydroboration of alkenen is an example of steropecific reaction, in which different steroisomers of starting compounds react to give different steroisomers of the product. CH_(3)-underset(CH_(3))underset(|)overset(CH_(3))overset(|)C-CH=CH_(2) underset((ii)H_(2)O_(2)//OH^(bar(..)))overset((i)BH_(3)//THF)rarrZ . Z is :

Calculate total entropy change for the transition of 1 mole of solid sulphur from its monoclinic form to the rhombic form at 400 K, id DeltaH=-400J//"mole" for this transition and assume the surrounding to be in a bath of water at 27^(@)C

Calculate change in enthalpy when 2 moles of liquid water at 1 bar and 100^(@) C is coverted into steam at 2 bar and 300^(@) . Assume H_(2)O vapoures to behave ideally. [Latent heat of vaporisation of H_(2)O(l) at 1 bar and 100^(@) C id=s 10.8 kcal per mole] [R= 2cal//"mol" K ]

Calculate the total entropy change for the transition at 368K of 1mol of sulphur from the monoclinic to the rhombic solid state, if DeltaH=-401.7J ,mol^(-1) "for the transition". Assume the surroundings tio be an ice-water bath at 0^(@)C :