What is eutectic reaction What is eutectoid reaction What is

What is eutectic reaction? What is eutectoid reaction? What is perifectic reaction? Are these transformations reversible? in the following phase diagrams (figure QB) these points from points A, B, C, D, E, F, G, H, K, and write down the reactions at these points. For example point A is perifectic reaction at this point can be written as Lipid and delta-iron transform to gamma-iron during cooling.

Solution

Eutectic reaction: A eutectic reaction is a reaction when one a liquid cools down into a mixture of two solids. Elements have different miscibility at different temperatures. So, when a liquid containing two elements soluble in one another cools down to a level where the solutbility is limited, then the excess element is sandwiched between the zones containing the mixture. This reaction is Eutectic reaction. In the Iron-Carbide diagram above, it is represented by the point D.

Eutectoid reaction: A eutectoid reaction is a reaction where one solid divides into a mixture of two solids. It has the same concept as eutectic reaction but here, instead of a liquid splitting up into two solids, a solid breaks down into two solids. For example, B is an eutectoid reaction

Peritectic reaction: A peritectic reaction is where the mixture of a solid and liquid combines into a single solid. Here, the miscibility is low when there is a phase-equilibrium between the liquid and the solid but as the temperature decreases, the solubility increases. Hence, it is completely miscible in the solid. For example, A shows the peritectic reaction happening.

Yes, since all the solutions are in a state of pahse equilibrium, they can be interchanged and the reaction can go either ways. It is completely reversible.