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#Ellingham diagrams free#

Say for example more than one oxide is possible. Also, it does not provide complete information about the oxides and their formations.It does not consider the kinetics of the reactions.And as a result, this curve will go downwards. 2C (s)+ O 2 (g) → 2CO (g): Here one mole of gas is giving you two moles of gas as products.So there will be no slope, it is completely horizontal. So here one molecule of gas is resulting in one molecule of gas. C(s) + O 2 (g) → CO 2 (g): Entropy of solids is negligible.There are cases when the entropy is not negative, and the slope will not be upwards. Hence as the temperature increases, the value of TΔS will also increase, and the slope of the reaction goes upwards Also since in the reaction (as seen above), we are going from the gaseous state to the solid state ΔS is also negative.

Now when reducing metal oxides the ΔH is almost always negative (exothermic) reaction. The reaction of metal with air can be generally represented as

Metals that have curves at the bottom of the diagram reduce the metals found more towards the top.

We will plot the temperature on the Y-axis and the ΔG on the X axis.

However, there is a condition here, that a phase change should not occur.

Even ΔS that is the entropy is unaffected by the temperature.

As you know the ΔH (enthalpy) is not affected by the temperature.

The slope of the curve is the entropy and the intercept represents the enthalpy.

Here ΔG is plotted in relation to the temperature.

Let us take a look at some important properties of the Ellingham Diagram This helps us to find the most suitable reducing agent when we reduce oxides to give us pure metals. In metallurgy, we make use of the Ellingham diagram to plot the reduction process equations. It is basically a graphical representation of Gibbs Energy Flow. Now to attain a negative value of ΔG (which is desirable) the value of the equilibrium must be kept positive.Īn Ellingham diagram shows the relation between temperature and the stability of a compound. It is calculated by dividing the active mass of products by the active mass of reactants.

#Ellingham diagrams free#

Another equation which relates the Gibbs Free Energy to the equilibrium constant is This changes very sharply when the state of the matter changes. ΔS is the Entropy or the randomness of molecules. So when the reaction is exothermic, it makes ΔG negative. Here a positive value will depict an endothermic reaction, while a negative value will be an exothermic reaction. We will now look at two equations to arrive at ΔG If this value of ΔG is negative then the reaction will occur spontaneously. In thermodynamics, whether a process will happen spontaneously or not will be determined by Gibbs Free Energy. The main thermodynamic concept we must concern ourselves with when it comes to metallurgy is Gibbs Free Energy. It also allows us to predict and measure these changes. Thermodynamics is the study of the energy transfer that occurs during chemical as well as physical changes. Thermodynamics is the branch of science that deals with a relationship between thermal energy i.e. And here is where the concept of thermodynamics exits. There is an overlap between the study of physics and chemistry, known as Physical Chemistry.