The rate constant for this first‑order reaction is
0.200
s
−
1
at
400

∘
C.

A
⟶
products

How long, in seconds, would it take for the concentration of
A
to decrease from
0.950
M
to
0.300
M?

t
=

s

t = 5.7634 s

Explanation:

∴ T = 400°C

∴ α = 1 first-order

∴ CAo = 0.950 M

∴ CA = 0.300 M

⇒ t = ?

⇒ - δCA/δt = K*CA

⇒ - ∫δCA/CA = K*∫δt

⇒ Ln (CAo/CA) = K*t

⇒ t = Ln(CAo/CA) / K

⇒ t = (Ln(0.950/0.300)) / (0.200 s-1)

⇒ t = 1.1527 / 0.200 s-1

⇒ t = 5.7634 s

4d^55s^1 ( third choice)