[student8607]

first order reaction
rate constant at 427k: 5.11x10^-5
initial concentration is 0.0340M


I know half life: 0.693/5.11x10^-5 = 1,3561sec --> 3.7hour
Is there a method for solving these above questions or is it just about estimation of what you know?


question 1: what is the molarity after 2.00hour?
I got about 0.0183 molar

question 2: how many minutes does it take for concentration to drop to 0.0300M?
I got about 1 minute

question 3: how many minutes does it take for 20% to react?
I got about 90.4 minutes

[TheJoker]

you probably used this but just in case ,   for 1st order reactions:

ln([A]at time t / [A]initial ) = -kt

[student8607]

Ahhhh. I knew there was an equation for that.

Thanks!