The initial concentration of Compound A is 1.5 mol/L. It disappears in a zero-order reaction with a rate constant of #"0.2 mol·L"^"-1""s"^"-1"#. What is its concentration after 15 s?
You use the integrated rate law for a zero order reaction:
[A] = [A]₀ - kt.
Insert the values of [A]₀, k and t into the equation and solve for [A].
You will get a value of -
It is impossible to have a negative concentration. This tells you that all the A has disappeared before 15 s.
If you set [A] = 0 and solve fot t, you get
All the A has vanished after 8 s, so there is none after 15 s.