The first-order rate constant for the decomposition of N2O5, 2N2O5(g)→4NO2(g)+O2(g) at 70∘C is 6.82×10−3 s−1. Suppose we start with 2.90×10−2 mol of N2O5(g) in a volume of 1.7 L.

Part A How many moles of N2O5 will remain after 4.0 min ?

Respuesta :

Answer:

0.00564 moles

Explanation:

Given that:

The rate constant, k = [tex]6.82\times 10^{-3}[/tex] s⁻¹

Initial concentration [A₀] = [tex]2.90\times 10^{-2}[/tex] mol

Time = 4.0 min = [tex]4.0\times 60[/tex] sec = 240 sec

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

So,  

[tex][A_t]=2.90\times 10^{-2}\times e^{-6.82\times 10^{-3}\times 240}=2.9\times \frac{1}{10^2}\times \frac{1}{e^{1.6368}}[/tex]

[tex][A_t]=0.00564\ moles[/tex]

The concentration after four minutes is 3.3 ×10−3.

Let us recall that for a first order reaction;

ln[A] = ln[A]o - kt

Where;

[A] = concentration at time t

[A]o = initial concentration

k = rate constant

t = time

[A]o = 2.90×10−2 mol/1.7 L = 0.0171 M

k = 6.82×10−3 s−1

t = 4 min or 240 s

Substituting values;

ln[A] = ln[0.0171 M] - (6.82×10−3 s−1 × 240 s)

[A]  = e^ln[0.0171 M] - (6.82×10−3 s−1 × 240 s)

[A]  = 3.3 ×10−3.

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