How long (in seconds) would it take for the concentration of A to decrease from 0.790 M to 0.270 M?

Question

Ch17Q15

The rate constant for this zero‑order reaction is 0.0340 M·s−10.0340 M·s−1 at 300 ∘C.300⁢ ∘C.

A⟶productsA⟶products

How long (in seconds) would it take for the concentration of AA to decrease from 0.790 M0.790 M to 0.270 M?0.270 M?

𝑡=__s

CH17Q16

The rate constant for the reaction is 0.310 M−1⋅s−10.310⁢ M−1⋅s−1 at 200 ∘C.200⁢ ∘C.

A⟶productsA⟶products

If the initial concentration of AA is 0.00820 M,0.00820 M, what will be the concentration after 485 s?485 s?



[A]=___M

Answer 1

Q15 For a zero order reaction the integrated rate law is as follows

[A] = −kt + [A]₀

Solving for t

t = ( [A]₀ - [A] ) / k 

Plugging in the numbers

k = 0.0340 M·s⁻¹

[A]₀ = 0.790 M

[A] = 0.270 M

t = ( 0.790 M - 0.270 M ) / ( 0.0340 M·s⁻¹ ) = (0.520 / 0.0340 ) s = 15.3 s

Q16 The units of the rate constant indicate a second order reaction, for which the integrated rate law is as follows

[A]^-1 = kt + [A]₀^-1

Plugging in the numbers

k = 0.310 M⁻¹·s⁻¹

[A]₀ = 0.00820 M

t = 485 s

[A]^-1 = 0.310 M⁻¹·s⁻¹ × 485 s + 0.00820 ⁻¹ M⁻¹ = 272 M⁻¹

[A] = 0.00367 M