Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Reaction Rate and Pressure

  1. Feb 8, 2015 #1
    The question is:

    The rate equation for the reaction A2 + B2 -> 2C (all gases) is rate = k[A2]2[B2]. If the gaseous reaction misture is compressed to half its original volume, by what factor will the reaction rate change. Assume temperature is constant.

    My thoughts are that the reaction rate wouldn't change. I know the rate changes if the concentrations of any of the reactants do, which is quite simple to calculate, but I'm not totally sure on pressure's effect on reaction rate. Any pushes in the right direction would be great.
     
  2. jcsd
  3. Feb 8, 2015 #2

    Borek

    User Avatar

    Staff: Mentor

    Imagine having 1 mole of an ideal gas squeezed into 1 L volume. What is its concentration?

    Apply twice the pressure. What is the volume now? What is the concentration now?
     
  4. Feb 8, 2015 #3
    Ah, I see. The concentration of both would be 2M, so substituting would give me:

    rate = 8k[A2]2][B2]

    Thanks for the help!
     
  5. Feb 8, 2015 #4

    epenguin

    User Avatar
    Homework Helper
    Gold Member

    No! The rate has increased by a factor of 8 but it's still k[A2]2][B2] , just each of the things inside the brackets has doubled.
     
  6. Feb 8, 2015 #5
    What do you mean by "it's"? The reaction rate doesn't increase by a factor of 8?
     
  7. Feb 8, 2015 #6

    epenguin

    User Avatar
    Homework Helper
    Gold Member

    Yes I said the reaction rate increases 8X. "It's" means "it is". :oldsmile:

    Consider [A2], [B2] to represent variables, k a constant.
     
    Last edited: Feb 8, 2015
  8. Feb 8, 2015 #7

    Borek

    User Avatar

    Staff: Mentor

    In other words, rate is in both cases k[A2]2[B2], but rate'=8*rate.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Reaction Rate and Pressure
  1. Rates of reaction? (Replies: 4)

  2. Reaction Rate (Replies: 5)

  3. Rates of reactions (Replies: 14)

  4. Reaction rate (Replies: 1)

  5. Rate of reaction (Replies: 7)

Loading...