The time taken or 25% of the molecules to desorb is 2.2 seconds
What is a first order reaction?
A first order reaction is one in which the rate of reaction depends on the concentration of a single specie.
Since;
t1/2 = 0.693/k = 0.693/ 0.128 s-1
t1/2 = 5.4 secs
Using the formula;
0.693/t1/2 = 2.303/t log (No/N)
0.693/5.4 = 2.303/t log 1/0.75
0.693/5.4 = 2.303/t log
0.693/5.4 = 0.287/t
t = 2.2 seconds
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