The half-life of the reaction is 101.9 min
When a reaction's pace and reactant concentration are inversely correlated, the process is known as a first-order reaction. To put it another way, the reaction rate doubles when the concentration does. One or two reactants can be present in a first-order reaction, as in the case of the decomposition process.
The amount of time it takes for the initial concentration of the reactant(s) to decrease by half is known as the half-life of a chemical reaction (abbreviated as "t1/2").
a→b
25% reacted means 75% remains
t=42 min
Rate constant
k=(2.303/t)(log a/a-x)
k=(2.303/42)(log 100/100-25 )
k=(0.054) (log 100/75)
k=(0.054)(0.1249)
k=0.0068 per min
half life
t1/2=(0.693/k)
=(0.693/0.0068)
=101.9 min
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