A student studies the bleaching of crystal violet (CV+) by NaOH using a spectrophotometer at 590 nm. With NaOH in large excess (pseudo-first-order), the absorbance is recorded versus time: t (s): 0 30 60 90 120 150 A: 0.800 0.610 0.464 0.353 0.269 0.205 A plot of ln(A) versus t is linear with slope = -0.00908 s^-1.
What is the half-life under these pseudo-first-order conditions?
- A
30 s
- B
0.0091 s
- C
108 s
- Dcheck_circle
76 s
Explanation
t1/2 = ln 2 / k_obs = 0.693 / 0.00908 = 76 s.