CBSE Updates

Pressure is directly proportional to temperature. As the temperature increases in summer, the pressure of the gas inside the bottle will increase. Morover the solubility of the dissolved gas decreases with increase in temperature. To avoid the bottles bursting open as a result of increase in pressure, they are kept in water. Water absorbs heat more slowly due to its higher latent heat of vapourisation.

Moles of CO2 produced during combustion of 35.2g carbon = 35.2/44--> 0.8mole

Enthalpy of combustion for 1 mole = -393.5kj

Enthalpy of combustion for 0.8 mole=0.8*-393.5--> 314.8 KJ

For diatomic molecules like H2, O2 N2 etc, the bond energy is equal to the dissociation energy, because these molecule has only bond no other things like angle, dihedral etc. For example in H2O molecule along with bond between H-O, there is a angle also between H-O-H which also contribute in the dissociation energy, and that is the reason why the bond energy cant be same as dissociation energy in multiatomic molecule. 

Entropy is a measure of disorder, or the energy loss in a process during its state changes in irreversible manner. A simple example of the entropy can be understood in the following way.

consider a non reversible process which can happen in many ways, e.g. Expanding a gas in cylinder from high pressure to low pressure. It is understood that this can happen in plenty of way by extracting a work from system. If we allow a sudden expansion of the gas, it will generate high entropy, however if we expand the gas with slow pressure changes then the entropy generated is less. In general an entropy can be considered as the degradation of the energy when high quality energy (mechanical) is converted in to low quality energy (heat) 

Free energy is amount of enegy have to the system for the reaction. Its changes will tell the direction and sponteneity of the reaction. If the change in free energy is positive for and process, the reaction or process will never occure. whereas, if is negative the reaction or process will happend sponneously ( means withou effort)