The first-order rate constant for the decomposition of N2O5, given below, at 70°C is 6.82 10-3 s-1. Suppose we start with 0.0200 mol of N2O5(g) in a volume of 2.5 L. 2 N2O5(g) → 4 NO2(g) + O2(g) (a) How many moles of N2O5 will remain after 2.5 min? mol (b) How many minutes will it take for the quantity of N2O5 to drop to 0.005 mol? min (c) What is the half-life of N2O5 at 70°C?

Respuesta :

Answer:

Explanation:

For first order reaction the equation is

[tex]k = \frac{1}{t} ln\frac{a}{a_t}[/tex]

k is rate constant , t is time , a is initial concentration and a_t is concentration after time t .

Putting the values

[tex]6.82\times 10^{-3} = \frac{1}{2.5\times 60} ln\frac{.02}{a_t}\\[/tex]

[tex]ln\frac{.02}{a_t}[/tex] = 1.023

.02 / a_t = 2.78

a_t = 7.2 x 10⁻³ moles

b ) Let after t time the mole becomes .005

again putting the values in the equation

[tex]6.82\times 10^{-3} = \frac{1}{t\times 60} ln\frac{.02}{.005}\\[/tex]

409.2 t x 10⁻³ = [tex]ln\frac{.2 }{.005\\}[/tex] = 3.689

t = 9.01 min

c ) for half life a_t = a / 2

putting the values in the equation

6.82 x 10⁻³ x 60 x t = ln 2

t = 1.7 min.

a). The number of moles remaining post 2.5 minutes would be:

[tex]= 7.2 [/tex] × [tex]10^{-3} moles[/tex]

b). The number of minutes required for  [tex]N_{2} O_{5}[/tex]'s quantity to fall to 0.005 moles would be:

[tex]= 9.01 min[/tex]

c). The half-life of [tex]N_{2} O_{5}[/tex] at 70°C would be:

[tex]= 1.7 minutes[/tex]

a). Given that,

The first-order rate of reaction for  [tex]N_{2} O_{5}[/tex] decomposition [tex]= 6.82[/tex] × [tex]10^{-3} s^{-1} [/tex]

Amount of  [tex]N_{2} O_{5}[/tex] [tex]= 0.0200 mol[/tex]

Volume of solution [tex]= 2.5 liters[/tex]

by using

[tex]k = (\frac{1}{t})In(\frac{a}{a_{1} })[/tex]

After applying the values to it, we get

[tex]= 6.82[/tex] × [tex]10^{-3} s^{-1} [/tex] [tex]= [1/(2.5 * 60)]In(.02/a_{t}) [/tex]

⇒ [tex].02 / a_t = 2.78[/tex]

∵ [tex]a_{t} [/tex]  [tex]= 7.2 [/tex] × [tex]10^{-3} moles[/tex]

b). The number of minutes required for  [tex]N_{2} O_{5}[/tex] quantity to fall to 0.005 moles would be:

Let t as the time,

[tex]= 6.82[/tex] × [tex]10^{-3} s^{-1} [/tex] [tex]= (1 /(t * 60) In (.02/.005)[/tex]

∵ [tex]t = 9.01 min[/tex]

c). The half-life of [tex]N_{2} O_{5}[/tex] at 70°C would be:

[tex]a_t = a / 2[/tex]

applying the values in the above equation

[tex]6.82 [/tex] ×[tex]10^{-3} [/tex] × [tex]60 [/tex] × [tex]t = In.2[/tex]

∵ [tex]t = 1.7 min[/tex]

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