[student8607]

CH₃NC(g) --> <--- CH₃CN(g)
obeys the first order rate law. At 500K, the concentration of CH₃NC is 85% of its original value after 247s. What is the rate constant at 500 K?

ln(Rt) = ln(Ro) - kt...where Ro is original concentration and Rt is concentration at the given time
**My main question is what to do with the percent.**


At what time will the concentration of CH₃NC be 25% of the original value?
I can use this equation....t_1/2 = 0.693/k

[Astrokel]

Same as the other post, don't ln the equation.

[student8607]

Not 100% sure I understand this one...

0.85= -247k
-0.00344=k?

antiln -->0.9965

[Astrokel]

0.85 = e^-kt

[student8607]

0.85 = e^-247k

But if I take the anti-ln of that right side I get 0?
So do I have to take the ln of 0.85 to cancel everything out?

[Astrokel]

But if I take the anti-ln of that right side I get 0?

huh?

0.85 = e^-247k
ln 0.85 = -247k
k = ...

[student8607]

6.57x10^-4