The half-life for beta decay of strontium-90 is 28.8 years. a milk sample is found to contain 10.3 ppm strontium-90. how many years would pass before the strontium-90 concentration would drop to 1.0 ppm?

Answer : The correct answer is 96.68 yrs

Radioactivity Decay :

it is a process in which a nucleus of unstable atom emit energy in form of radiations like alpha particle , beta particle etc .

Radioactive decay follows first order kinetics , so its rate , rate constant , amount o isotopes can be calculated using first order equations .

The first order equation for radioactive decay can be expressed as :

----------- equation (1)

Where : N = amount of radioisotope after time "t"

N₀ = Initial amount of radioisotope

k = decay constant and t = time

Following steps can be used to find time :

1) To find deacy constant :

Decay constant can be calculated using half life . Decay constant and half life can be related as :

---------equation (2)

Given : Half life of Strontium -90 = 28.8 years

Plugging value of in above formula (equation 2) :

Multiply both side by k

Dividing both side by 28.8 yrs

(ln 2 = 0.693 )

k = 0.0241 yrs⁻¹

Step 2 : To find time :

Given : N₀ = 10.3 ppm N = 1.0 ppm k = 0.0241 yrs⁻¹

Plugging these value in equation (1) as :

(ln 0.0971 = - 2.33 )

Dividing both side by - 0.0241 yrs⁻¹

t = 96.68 yrs

Hence the concentration of Strontium-90 will drop from 10.3 ppm to 1.0 ppm is 96.68 yrs

96.9 years

Given:

Question:

How many years would pass before the strontium-90 concentration would drop to 1.0 ppm?

The Process:

In the calculations of half-lives, the expressions are the following:

where are used. In these expressions;

Step-1: find out the number of half-lives (n)

We get n = 3.364572

Step-2: find out in how many years would pass before the strontium-90 concentration would drop to 1.0 ppm

t = 3.364572 x 28.8

t = 96.9

Thus in 96.9 years will pass before the concentration of strontium-90 will drop to 1.0 ppm.

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Notes:

The half-life of radioactive decay is the period of time required for half of the initial amount of the substance to disintegrate. The shorter the half-life of radioactive decay, the higher the rate of radioactive decay and the more radioactivity. The half-life is the characteristic property of each element.

answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

that's it!

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~ trueboss72