Aradioisotope is placed near a radiation detector, which registers 64 counts per second. eight hours later, the detector registers 8 counts per second. what is the half-life of the radioactive isotope?

Answer : The half life of the radioisotope is 2.7 hours.

Explanation :

Radioactive disintegration is a first order reaction. The disintegration equation can be written as,

Here N is the amount of radioactive substance left = 8 counts

No is the initial amount of Radioactive substance = 64 counts

t is the time = 8 hours

λ is the disintegration constant

Let us rearrange the equation to solve for λ

Take natural logarithm "ln" on both sides

Divide both sides by t

Let us plug in the given values.

The disintegration constant, λ is 0.26.

λ and half life ( t1/2) are related to each other by following equation.

Let us plug in the value of λ

The half life of the radioisotope is 2.7 hours.

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.

the transfer of heat by electromagnetic radiation is called thermal radiation . it is usually carried out by electromagnetic waves in an energy range just below the visible spectrum, which is the infrared range.

so the answer would be radiation.

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