Welcome to Chemistry Stack Exchange

Chemistry is a question and answer site for scientists, academics, teachers and students of chemistry. It's built and run by you as part of the Stack Exchange network of Q&A sites. With your help, we're working together to build a library of detailed answers to every question about chemistry.

We're a little bit different from other sites. Here's how:


Ask questions, get answers, no distractions

This site is all about getting answers. It's not a discussion forum. There's no chit-chat.

Just questions...

...and answers.

up vote

Good answers are voted up and rise to the top.

The best answers show up first so that they are always easy to find.

accept

The person who asked can mark one answer as "accepted".

Accepting doesn't mean it's the best answer, it just means that it worked for the person who asked.

What is the molecularity of a reversible reaction?

up vote 14 down vote favorite

I know that the definition of molecularity of a reaction is number of species reacting in an elementary step. But considering the theory of microscopic reversibility for elementary reactions, each reaction can be assumed to be reversible. In that case, if $$\ce{A <=> B + C}$$ then what is the molecularity of the reaction? Is it 1 or 2?

2 Answers

up vote 4 down vote accept

For the reaction $$\ce {A <=> B + C}$$ its molecularity is unimolecular. If we were given $$\ce{B + C <=> A}$$ Its molecularity would be bimolecular. Thus we see molecularity is dependent on the number of reactant particles, even if it's in equilibrium.

up vote 3 down vote

Just to add onto the other answer.
Since the equilibrium constant also changes when we reverse a reaction, so does the molecularity of the reaction.
So many properties of reversible reactions are defined in the way we write down the reaction.


Get answers to practical, detailed questions

Focus on questions about an actual problem you have faced. Include details about what you have tried and exactly what you are trying to do.

Ask about...

  • Chemistry concepts
  • Observed chemical phenomena
  • Experimental techniques and technology
  • Nomenclature, standards, etc. pertaining to chemistry

Not all questions work well in our format. Avoid questions that are primarily opinion-based, or that are likely to generate discussion rather than answers.

Questions that need improvement may be closed until someone fixes them.

Don't ask about...

  • Homework (read the homework policy if you have such a question)
  • Personal medical questions
  • Legal questions relating to chemical substances and techniques
  • Non-mainstream chemistry
  • Computational questions
  • Anything not directly related to chemistry
  • Questions that are primarily opinion-based
  • Questions with too many possible answers or that would require an extremely long answer

Tags make it easy to find interesting questions

All questions are tagged with their subject areas. Each can have up to 5 tags, since a question might be related to several subjects.

Click any tag to see a list of questions with that tag, or go to the tag list to browse for topics that interest you.

What is the molecularity of a reversible reaction?

up vote 14 down vote

I know that the definition of molecularity of a reaction is number of species reacting in an elementary step. But considering the theory of microscopic reversibility for elementary reactions, each reaction can be assumed to be reversible. In that case, if $$\ce{A <=> B + C}$$ then what is the molecularity of the reaction? Is it 1 or 2?


You earn reputation when people vote on your posts

Your reputation score goes up when others vote up your questions, answers and edits.

+5 question voted up
+10 answer voted up
+15 answer is accepted
+2 edit approved

As you earn reputation, you'll unlock new privileges like the ability to vote, comment, and even edit other people's posts.

Reputation Privilege
15 Vote up
50 Leave comments
125 Vote down (costs 1 rep on answers)

At the highest levels, you'll have access to special moderation tools. You'll be able to work alongside our community moderators to keep the site focused and helpful.

2000 Edit other people's posts
3000 Vote to close, reopen, or migrate questions
10000 Access to moderation tools
see all privileges

Improve posts by editing or commenting

Our goal is to have the best answers to every question, so if you see questions or answers that can be improved, you can edit them.

Use edits to fix mistakes, improve formatting, or clarify the meaning of a post.

Use comments to ask for more information or clarify a question or answer.

You can always comment on your own questions and answers. Once you earn 50 reputation, you can comment on anybody's post.

Remember: we're all here to learn, so be friendly and helpful!

up vote 9 down vote

For the reaction $$\ce {A <=> B + C}$$ its molecularity is unimolecular. If we were given $$\ce{B + C <=> A}$$ Its molecularity would be bimolecular. Thus we see molecularity is dependent on the number of reactant particles, even if it's in equilibrium.

edit

Here also the use of the arrows is wrong, see my comment to the question. - Martin - γƒžγƒΌγƒγƒ³ May 5 '15 at 14:34

add comment


Unlock badges for special achievements

Badges are special achievements you earn for participating on the site. They come in three levels: bronze, silver, and gold.

In fact, you can earn a badge just for reading this page:

 Informed Read the entire tour page
 Student First question with score of 1 or more
 Editor First edit
 Good Answer Answer score of 25 or more
 Civic Duty Vote 300 or more times
 Famous Question Question with 10,000 views

see all badges


Sign up to get started

Signing up allows you to:

  • Earn reputation when you help others with questions, answers and edits.
  • Select favorite tags to customize your home page.
  • Claim your first badge:  Informed
Looking for more in-depth information on the site? Visit the Help Center

Chemistry Stack Exchange is part of the Stack Exchange network

Like this site? Stack Exchange is a network of 152 Q&A sites just like it. Check out the full list of sites.

Stack Exchange