Chemistry help!!?
2020-04-12 1:45 pm
A certain substance, initially present at 0.950 M, decomposes by first-order kinetics with a rate constant of 1.25 × 10-2 mol L-1s-1. Calculate the time (in seconds) required for the system to reach a concentration of 0.726M.
回答 (1)
2020-04-12 2:34 pm
Method 1:
Integrated rate equation for first-order reaction:
ln[A] = -kt + ln[A]ₒ
ln(0.726) = -(1.25 × 10⁻²)t + ln(0.950)
t = [ln(0.950) - ln(0.726)] / (1.25 × 10⁻²) s
Time taken, t = 21.5 s
====
Method 2:
Half-life = ln(2)/k = ln(2)/(1.25 × 10⁻²) s = 55.45 s
Let n be the number of half-life.
0.726 = 0.950 × (1/2)ⁿ
0.5ⁿ = 0.726/0.950
log(0.5ⁿ) = log(0.726/0.950)
n log(0.5) = log(0.726/0.950)
n = log(0.726/0.950) / log(0.5)
n = 0.3880
Time taken = (55.45 s) × (0.3880) = 21.5 s
Integrated rate equation for first-order reaction:
ln[A] = -kt + ln[A]ₒ
ln(0.726) = -(1.25 × 10⁻²)t + ln(0.950)
t = [ln(0.950) - ln(0.726)] / (1.25 × 10⁻²) s
Time taken, t = 21.5 s
====
Method 2:
Half-life = ln(2)/k = ln(2)/(1.25 × 10⁻²) s = 55.45 s
Let n be the number of half-life.
0.726 = 0.950 × (1/2)ⁿ
0.5ⁿ = 0.726/0.950
log(0.5ⁿ) = log(0.726/0.950)
n log(0.5) = log(0.726/0.950)
n = log(0.726/0.950) / log(0.5)
n = 0.3880
Time taken = (55.45 s) × (0.3880) = 21.5 s
收錄日期: 2021-04-18 18:28:26
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20200412054503AAI4j5d