The initial mass of a radioisotope is 15.0 g. If the radioisotope has a half-life of 2.75 years, how much remains after four half-lives?

0.9375 grams

Explanation:

As we know half life is the time period in which quantity of a substance reduces to half of its original value.

The formula to calculate amount of substance left after n half life is

where x is the amount of original substance

n is the no of half life.

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Given

No. of half lives = 4

amount of original substance = 15 gram

thus,

n = 4

x = 15 grams

amount of radioisotope left after 4 half life =

Thus, only 0.9375 grams of radioisotope are left after 4 half lives.

answer: -

reaction:

na + cl ⇌ nacl

balanced chemical equation:

na + 2cl ⇌ nacl2

sodium + clorine goes to form sodium chloride (table salt).

the product is nacl2.

and the reactants are na and cl.

(note: if you don’t know what ⇌ means, read below: -

⇌(double head arrow) means reversible reaction).