Answer: Number of half lives occurred 2.
Explanation:
Let the initial concentration be x
Concentration left=25 % of the x= [tex]x\frac{25}{100}=\frac{x}{4}[/tex]
To calculate the number of half lives, we use the formula:
[tex]a=\frac{a_o}{2^n}[/tex]..(1)
where,
a = amount of reactant left after n-half lives = 0.0495 moles
[tex]a_o[/tex] = Initial amount of the reactant = 0.7924 moles
n = number of half lives
[tex]\frac{x}{4}=\frac{x}{2^n}[/tex]
taking log both sides
[tex]\logx-\log4=\logx-n\log2[/tex]
[tex]\log4=n\log2[/tex]
[tex]\log(2)^2=2\log2=n\log2[/tex]
n = 2
Number of half lives occurred 2.
