A + 2B → AB A) Unimolecular B) Bimolecular C) Termolecular D) Tetramolecular E)

Question

Given the following elementary reaction what is the molecularity? A + 2B → AB₂

A) Unimolecular

B) Bimolecular

C) Termolecular

D) Tetramolecular

E) Can not be determined with the given information

Answer 1

Hi Ina S.,

Your work has been done for you. When the reaction was characterized as "elementary", that indicated that you just count the number of molecules that had to come together as written. That was one A, and 2 B's, for a total of 3 == Termolecular.

Note that if the elementary reaction had been listed as A + B₂ = AB₂ , that would only be a bimolecular reaction, there were only one A and one B₂ that merged.

It matters, because bimolecular processes are FAR more abundant that TER, which are far more abundant that TETRA, and so on. Therefore, whenever possible, nature chooses reactions along bimolecular paths -- no matter how many atoms take part overall in a reaction.

But, once you have the reactants and products of a reaction written, the position of equilibrium of the reaction (how much of various "reactants" and "products" remain after they work out their energy and entropy together) depends not at all on the mechanism between, only on the overall reaction co-efficients. You will learn all of this, and more ....

--Cheers, --Mr. d.