The rate constant for this first‑order reaction is 0.0350 s − 1 0.0350 s−1 at 400 ∘ C. 400 ∘C. A ⟶ products A⟶products After how many seconds will 18.1 % 18.1% of the reactant remain?

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Answer:

After 48.84 s, 18.1% of the reactant will remain.

Explanation:

Given that:

The rate constant, k = 0.0350 s⁻¹

Using integrated rate law for first order kinetics as:

[tex][A_t]=[A_0]e^{-kt}[/tex]

Where,  

[tex][A_t][/tex] is the concentration at time t

[tex][A_0][/tex] is the initial concentration

Given:

18.1 % of the reactant remain which means that 0.181 of [tex][A_0][/tex] is remained. So,

[tex]\frac {[A_t]}{[A_0]}[/tex] = 0.181

t = ?

[tex]\frac {[A_t]}{[A_0]}=e^{-k\times t}[/tex]

[tex]0.181=e^{-0.0350\times t}[/tex]

t = 48.84 s

After 48.84 s, 18.1% of the reactant will remain.

18%  of the starting material will remain after 49 seconds.

What is rate of reaction?

The term rate of reaction refers to how quickly a reaction proceeds. This reaction as we are told follows first order kinetics.

We can use the formula;

0.693/t1/2 = 2.303/tlog (No/N)

Given that t1/2 = 0.693/k = 0.693/0.0350 s − 1 =19.8 seconds

So;

0.693/19.8 = 2.303/t log 1/0.181

0.693/19.8 = 1.71/t

t = 1.71/0.035

t = 49 seconds

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