A radioactive element of mass 1g has half-life of 2 minutes, what fraction of the substance would have disintegrated after 10 minutes?

Assessment: JAMB UTME - Chemistry - 2024 Subject: Chemistry

Question 1 Report

1/4

1/8

1/16

1/32

Answer Details

$\frac{O r i g i n a l m a s s}{2^{n}}$ = Residual mass

Where n = number of activity = $\frac{e x p o s u r e t i m e}{h a l f l i f e}$

Given:

Original mass = 1g, exposure time = 10 minutes , half life = 2 minutes, Residual mass = ?

Substituting all the given parameters appropriately, we have

n = $\frac{10}{2}$

n = 5

$\frac{O r i g i n a l m a s s}{2^{n}}$ = Residual mass

$\frac{1}{2^{5}}$ = Residual mass

$\frac{1}{32}$ = Residual mass

Residual mass = $\frac{1}{32}$ or 0.03125g

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