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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: 777888 on November 20, 2004, 06:18:20 PM

Title: Equilibrium law in chemical reactions
Post by: 777888 on November 20, 2004, 06:18:20 PM: Hi, I have some questions:

1)What is the Law of Mass Action"?

2)What is the realationship known as "Equilibrium Law"?

[Is there a difference between question 1 and 2? They seem like the same question...]

3)Write the law of mass action for the reaction: H2 + I2 = 2HI
[What is this trying to ask? Is the answer a number? How can I write this law?]
Title: Re:Equilibrium law in chemical reactions
Post by: ssssss on November 21, 2004, 02:11:21 AM: Quote from: 777888 on November 20, 2004, 06:18:20 PM
Hi, I have some questions:

1)What is the Law of Mass Action"?

2)What is the realationship known as "Equilibrium Law"?

[Is there a difference between question 1 and 2? They seem like the same question...]

3)Write the law of mass action for the reaction: H2 + I2 = 2HI
[What is this trying to ask? Is the answer a number? How can I write this law?]

You are asking questions as you dont have a chemistry Book.These are basic principles given in your book in chapter on Chemical Equilibrium.Read it thoroughly.Then if you find any queries,Ask.
Title: Re:Equilibrium law in chemical reactions
Post by: 777888 on November 21, 2004, 02:15:56 AM: ...
Sorry, I read it but the textbook put law of mass action and equilibrium in the same place! I don't know if the law of mass action means the equation...
Title: Re:Equilibrium law in chemical reactions
Post by: Donaldson Tan on November 21, 2004, 08:32:50 AM: aA + bB -> cC + dD

Law of Mass Action tells you that [C]^c[D]^d/[A]^a^b = constant only if the the above reaction is at chemical equilibrium, ie.

aA + bB <-> cC + dD

The equilibrium law is a specific form of the law of mass action. The equilibrium law tells you that for a chemical system at equilibrium, its equilibirum constant can be computed as [C]^c[D]^d/[A]^a^b. Law of Mass Action confirms that this value is indeed a constant.
Title: Re:Equilibrium law in chemical reactions
Post by: 777888 on November 22, 2004, 01:06:16 AM: I am OK with this question now...we treat law of mass action and equilibrium law as the same thing
Title: Re:Equilibrium law in chemical reactions
Post by: 777888 on November 22, 2004, 10:12:04 AM: I have another question!

Are all / most reactions equilbrium reactions? Is there a case that is not a equilibrium reaction?
Title: Re:Equilibrium law in chemical reactions
Post by: jdurg on November 22, 2004, 10:53:57 AM: Quote from: 777888 on November 22, 2004, 10:12:04 AM
I have another question!

Are all / most reactions equilbrium reactions? Is there a case that is not a equilibrium reaction?

ALL reactions are equillibrium reactions. Every single one of them. It's just that for some reactions the equillibrium is favored towards the products so heavily that we say they are essentially all "forward reactions". (Such as the combustion of oxygen and hydrogen. The equillibrium constant favors the formation of water so much that we can disregard the infentesimally small handful of water molecules which decompose back into hydrogen and oxygen).
Title: Re:Equilibrium law in chemical reactions
Post by: 777888 on November 22, 2004, 12:38:21 PM: Thanks a lot~
Title: Re:Equilibrium law in chemical reactions
Post by: Mitch on November 22, 2004, 02:06:30 PM: All reactions are equilibrium reactions except those that are thermodynamically/photochemically forbidden of course.