# Problem: The desorption (leaving of the surface) of a single molecular layer of n-butane from a single crystal of aluminum oxide was found to be first order with a rate constant of 0.128/s at 150 K.If the surface is initially completely covered with n-butane at 150 K, how long will it take for 25% of the molecules to desorb (leave the surface)?

###### FREE Expert Solution

We’re being asked to determine the time it would take for 25% of the molecules to desorb (leave the surface)

The integrated rate law for a first order reaction is as follows:

where:

[A]t = concentration at time t,

[A]0 = initial

k = rate constant,

t = time

Since no concentration is given, we can use the given percentages in place of concentration.

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###### Problem Details

The desorption (leaving of the surface) of a single molecular layer of n-butane from a single crystal of aluminum oxide was found to be first order with a rate constant of 0.128/s at 150 K.

If the surface is initially completely covered with n-butane at 150 K, how long will it take for 25% of the molecules to desorb (leave the surface)?