Question

Which of the following is irreversible reaction
(1) $P{Cl}_5\to P{Cl}_3+{Cl}_2$
(2) $2{SO}_2+O_2\to 2{SO}_3$
(3) $N_2+3H_2\to 2{NH}_3$
(4) $2KCl{O}_3\to 2KCl+3O_2$

Answer 1

Solution:
potassium chlorate, or ${KClO}_3$, undergoes thermal decomposition to form potassium chloride,$KCL$, and oxygen gas,$O_2$.
Decomposition reaction will leave behind products that are as stable as possible. Heat is used to break the bonds of a compound, after which new bonds will be formed between the elements that formed the original compound. In the case of potassium chlorate,intense heating will produce a very stable ionic compound, potassium chloride, in solid state.
Hence (4) reaction is irreversible