Question

Solid 1 + Solid 2 $\rightarrow$ Solid 3 (during cooling) denotes

• A. Eutectic reaction
• B. Peritectic reaction
• C. Eutectoid reaction
• D. Peritectoid reaction

Hint:

Remember: {Peritectoid = Solid + Solid $\rightarrow$ Solid}.

Answer 1

The Correct Option is D

Step 1: Understanding invariant reactions.
Invariant reactions involve transformation of phases at a fixed temperature and composition in phase diagrams. These reactions may occur in liquid–solid or solid–solid systems.
Step 2: Identifying the given reaction.
The reaction given is: \[ \text{Solid 1} + \text{Solid 2} \rightarrow \text{Solid 3} \] This indicates a solid–solid reaction during cooling.
Step 3: Differentiating between reactions.
Eutectic: Liquid $\rightarrow$ Solid 1 + Solid 2
Peritectic: Liquid + Solid $\rightarrow$ Solid
Eutectoid: Solid $\rightarrow$ Solid 1 + Solid 2
Peritectoid: Solid 1 + Solid 2 $\rightarrow$ Solid 3
Step 4: Conclusion.
Thus, the given reaction represents a peritectoid reaction.