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:

A → Pdts - rA = K (CA) ∧α = - δCA/δt

∴ 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