Posted by biggie on Saturday, April 10, 2010 at 12:43pm.
In a first order decomposition reaction, 50% of a compound decomposes in 10.5 min. What is the rate constant of the reaction? How long does it take for 75% of the compound to decompose?
My professor did this problem in class:
k = .693 / 10.5 mins
= .066 min ^1
where did .693 come from?
Thanks

Chemistry  biggie, Saturday, April 10, 2010 at 12:46pm
it's from the halflife formula for first order process rate t1/2 = .693 / k

Chemistry  DBob222, Saturday, April 10, 2010 at 12:50pm
0.693 is the natural log of 2.
It comes from using the expression
ln(No/N) = kt
ln(100/50) = k*t_{1/2}
ln 2 = k*t<sub<1/2
k = ln2/t_{1/2} and
k = 9.693/t_{1/2}
The No/N I used above as 100 and 50 can be any number choose as long as N is 1/2 of No.
Answer This Question
Related Questions
 Chemistry  Problem: In a first order decomposition reaction, 50% of a compound ...
 Chemistry  What is the value of the rate constant for a reaction in which 75.0 ...
 Chemistry  What is the value of the rate constant for a reaction in which 75.0 ...
 HalfLife  Can someone please show me a detailed solution to this problem? ...
 Chemistry  Time, (min): 0 10 20 30 Moles,(trans): 1.00 0.90 0.81 0.73 Given the...
 Chemistry  A reaction is first order and it takes 324 minutes for the reaction ...
 chemistry kinetics  Decomposition of an organic compound A follows first order ...
 Chemistry  a certain first order decomposition reaction has a halflife of 15.0...
 Chemistry  Dinitrogen pentoxide, N2O5, decomposes by a firstorder reaction. ...
 chemistry  If the halflife of a firstorder decomposition reaction is 24.2 ...
More Related Questions