Question

.9)If the half life of a first order reaction is 15 min, then how much fraction of the reactant remains unreacted after 45 min?
1/4
1/8
1/16
1/32​

Answer 1

Answer:

1/8

PLZ:

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Shortcut:

fraction of the reactant remains unreacted after nthalfs=$(\frac{1}{2} )^{n}$

Explanation:

number of thalfs( n )=45/15=3

fraction of the reactant remains unreacted after 45 min=$(\frac{1}{2} )^{3}$=$\frac{1}{8}$

Answer 2

Answer:

The correct answer is Option B : $\frac{1}{8}$

Explanation:

A very simple and easy to solve this answer would be :

Fraction of the reactant which remains unreacted after n halfs : $(\frac{1}{2})^n$

Number of halfs in the given question :

$\frac{45}{15} =3$

Therefore the fraction of the reactant which remains unreacted after $45$ mins is $=(\frac{1}{2})^3$

$=\frac{1}{8}$

Half-life : The half-life of a quantity is the time it takes to reduce to half of its initial value.

In nuclear physics, the term is commonly used to describe how quickly unstable atoms undergo radioactive decay or how long stable atoms survive.