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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: student8607 on February 01, 2009, 12:52:15 PM

Title: Reaction rates & Rate constants
Post by: student8607 on February 01, 2009, 12:52:15 PM

A certain first-order reaction has a rate constant of 1.0x10^-3s^-1 at 25 degrees C.

If the reaction rate doubles when the temperature is increased to 35 degrees C, what is the activation energy in kJ?

I am familiar with the equation to solve for Ea but how am I to determine my second rate constant just from knowing the reaction rate doubles?

Title: Re: Reaction rates & Rate constants
Post by: Yggdrasil on February 01, 2009, 12:56:20 PM

You know that k₃₅ / k₂₅ = 2.  Can you write this ratio of rate constants in terms of activation energy?

Title: Re: Reaction rates & Rate constants
Post by: student8607 on February 02, 2009, 07:20:14 PM

If the rate doubles then the rate constant does as weel?

Ln(1.0x10-3 / 2.0x10-3) = -Ea/8.31 x (1/308 - 1/298)

?

Title: Re: Reaction rates & Rate constants
Post by: Yggdrasil on February 02, 2009, 10:45:41 PM

I would assume that is what the problem means, although doubling the rate constant is not the only way to double the rate of reaction.

Title: Re: Reaction rates & Rate constants
Post by: student8607 on February 03, 2009, 01:09:38 PM

Ok, will go with that.
Thanks!