In a first-order decomposition reaction, 50.0% of a compound decomposes in 19.5 min.


(a) What is the rate constant of the reaction? (round to four decimal places)

k = .03554 min−1

(b) How long does it take for 82.0% of the compound to decompose? (round to one decimal place)

t = ? min

1 answer

In a first-order decomposition reaction, 50.0% of a compound decomposes in 19.5 min.

(a) What is the rate constant of the reaction? (round to four decimal places)

k = .03554 min−1
That's right but didn't you round to 5 decimal places? four significant figures.

(b) How long does it take for 82.0% of the compound to decompose? (round to one decimal place)

t = ? min
ln(No/N) = kt
No = 100% to start
N = 18% (100% - 82% = 18%)
k = from above
Solve for t in minutes. Post your work if you get stuck.