March 28, 2017

Post a New Question

Posted by on .


In a first order decomposition reaction, 50% of a compound decomposes in 10.5 minutes. What is the rate constant of the reaction?

The solution my professor gave says:

k = .693 / 10.5min

Where did the .693 come from?


  • Chemistry - ,

    That is the natural logarithm of 2. You can do it this way.
    Let's start with 100 atoms of something.
    No = 100. Since it is 50% decomposed in 10.5 min, then 10.5 is the half-life and N at the end of that time will be 50.
    So ln(No/N) = kt
    ln(100/50) = k*t1/2
    ln(2) = k*t1/2
    0.693 = k*t1/2 and
    k = 0.693/t1/2

Answer This Question

First Name:
School Subject:

Related Questions

More Related Questions

Post a New Question