The gas-phase decomposition of CH3CHO (g) occurs according to the equation
CH3CHO (g) ----> CH4 (g) +CO (g) and is second order. The value of the rate constant is 0.105 M-1 x s-1 at 490 degrees Celcius. If the concentration of CH3CHO (g) is 0.012 M initially, what will be its concentration 5.0 minutes later.

Respuesta :

Answer:

Concentration of CH3CHO  5.0 minutes later is

[tex][A] =8.71\times 10^{-3}[/tex]M or 0.00871 M

Explanation:

The concentration for second order reaction can be calculated using the formula:

[tex]\frac{1}{[A]}=\frac{1}{[A_{0}]}+kt[/tex]

Here , [A] = Concentration of substance at time t

t = time

[tex][A_{0}][/tex] = Initial concentration

k = rate constant

According to question :

[A]  = Concentration of CH3CHO at time 5.0s = ?

[tex][A_{0}][/tex] = 0.012 M

t = 5.0 min

Convert it into second (because rate constant units are in second)

1 min = 60 s

t = 5 x 60 = 300 s

k = 0.105 M-1 s-1

Insert these value into,

[tex]\frac{1}{[A]}=\frac{1}{[A_{0}]}+kt[/tex]

[tex]\frac{1}{[A]}=\frac{1}{0.012}+ 0.105\times 300[/tex]

[tex]\frac{1}{[A]}=83.33+ 31.5[/tex]

[tex]\frac{1}{[A]}=83.33+ 31.5[/tex]

[tex]\frac{1}{[A]}=114.83[/tex]

[tex][A] =\frac{1}{114.83}[/tex]

[tex][A] =8.71\times 10^{-3}[/tex]M

Hence ,concentration of CH3CHO  5.0 minutes later is

[tex][A] =8.71\times 10^{-3}[/tex]M or 0.00871 M

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