7B.9

[haley f]

For the first-order reaction A → 3 B + C, when =[A]0=0.015 mol⋅L−1, the concentration of B increases to 0.018 mol⋅L−1 in 3.0 min. (a) What is the rate constant for the reaction expressed as the rate of loss of A? (b) How much more time would be needed for the concentration of B to increase to 0.30 mol⋅L−1?

I can't seem to get this problem right and I can't seem to figure out what I am doing wrong, can someone please walk me through it?

[Steph Du 1H]

It tells you how the concentration of B increases in 3 mins. Convert that to the rate at which the concentration of A decreases in 3 mins, subtract that from the initial [A} and you have your final [A] (it will be 0.009). Then use the integrated rate law for a 1st order reaction to get k. The same approach works for b. Also there is a typo for b, it is actually 0.030 M.

[Nico Medina]

I was wondering this too, thanks for the help!