Another thermodynamic quantities that helps in predicting the spontaneity of a process is Gibbs free energy or Gibbs energy of Gibbs function. It is denoted by G and is given by the equation G=H -TS where H is the heat content ,T is the absolute temperature and S is the entropy of the system. G1 =…
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Entropy
Entropy Entropy is a measure of randomness or disorder of the system. The greater the randomness, higher is the entropy. Solid state has the lowest entropy, the gaseous state has the highest entropy and the liquid state has the entropy in between the two. Entropy is a state function. The change in its value during…
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A process which under some conditions may take place by itself or by initiation independent of the rate is called spontaneous process. A process which can take place by itself or has an urge or tendency to take place is called spontaneous process. A spontaneous process is simply a process which is feasible. The rate…
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Bond energy is the amount of energy released when 1 mole of bonds are formed from the isolated atoms in the gaseous state or the amount of energy required to dissociate one mole of bonds present between the atoms in the gaseous molecules. It is represented by Δ b H or Δbond H. For diatomic molecules like H2,…
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Enthalpy of fusion Enthalpy of fusion is the enthalpy change accompanying the transformation of one mole of a solid substance into its liquid state at its melting point. it is also called molar enthalpy of fusion. The molar enthalpy of fusion ( Δ fus H ) of ice is +6 KJ mol-1. H2O ( s )…
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Heat of reaction or enthalpy of reaction is a term used for the heat changes accompanying any reaction. Enthalpy of combustion The enthalpy of combustion of a substance is defined as the heat change when 1 mole of substance is completely burnt or oxidised in oxygen. CH4 ( g ) + 2O2 ( g )…
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When a balanced chemical equation not only indicates the quantities of the different reactants and products but also indicates the amount of heat evolved or absorbed, it is called thermochemical equation. Fractional coefficients may be used in writing a thermochemical equation. H2 ( g ) + ½ O2 ( g ) ———> H2O ( l )…
Read MoreExothermic And Endothermic Reaction
Exothermic reactions These are those reactions which are accompanied by the evolution of heat. The quantity of heat produced is shown along with the products with a plus sign. For Ex: C ( s) + O2 (g) ——> CO2 ( g) + 395.3 kJ H2 (g) + ½ O2 (g) ——–> H2O ( l ) +…
Read MoreMeasurement Of Change In Internal Energy and Enthalpy
The experimental technique of measuring energy changes accompanying any chemical or physical process is called calorimetry. These measurements are generally carried out under 2 condition 1)at constant volume ( ΔU or qv ) 2)at constant pressure ( ΔH or qp) Measurements of ΔU Internal energy change is measured experimentally using an apparatus called Bomb calorimeter. It consists of…
Read MoreHeat Capacity
Heat capacity of a system is defined as the amount of heat required to raise the temperature of the system through 1°C . If q is the amount of heat supplied to a system and as a result ,if the temperature of the system rises from T1 and T2 ,then the heat capacity of the…
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According to first law of thermodynamics, q= ΔU + PΔV If the process is carried out at constant volume , ΔV=0 qv = ΔU where v indicates constant volume. Internal energy change is the heat absorbed or evolved at constant volume. ΔU is a state function, therefore qv ,is also a state function. If the process is…
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Internal Energy Whenever some process occur ,it is usually accompanied by some energy change. The energy may appear in different forms such as heat ,light ,work. The evolution or absorption of energy in different processes shows that every substance must be associated with some definite amount of energy ,the actual value of which depends upon…
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