A radioactive isotope of mercury, 197Hg, decays togold, 197Au, with a disintegration constant of 0.0108 h-1. What fraction of a sample will remain at the end of three half-lives (

THE FRACTION OF THE SAMPLE REMAINING AFTER THREE HALF LIVES IS 0.125 OR 125/1000

Explanation:

A radioactive isotope of mercury decay to gold with a disintegration constant of 0.0108 h^-1

To calculate the fraction of sample remaining after three half life, we first calculate the half life of the decay.

Half life = ln 2 / Y

Y = disintegration constant

So therefore,

half life = ln 2 / 0.0108

half life = 0.693 / 0.0108

half life = 64.18 hours.

So a decay occurs after 64.18 hours.

To calculate the fraction remaining after 3 half life:

N(t) = N(o) e ^-Yt

where t = 3 half life

So, N / No = e^-Y ( 3 t1/2)

Since t 1/2 = ln 2 / Y, so we can re-write the formula as:

Nt / No = e^-Y ( 3 ln 2/ Y)

Nt / No = e^-3 ln2

Nt / No = e^-3 * 0.693

Nt / No = e^-2.079

Nt / No = 0.125

So the fraction of the sample remaining after 3 half lives is 125/ 1000 or 0.125

number of molecules / avogadro's number * molecule molecular = mass

explanation:

we define a gram-molecular weight as the mass of one mole of any element or compound. a mole contains avogadro's number of units (molecules) –  

6.022

x

10

23

. so, dividing the number of molecules by avogadro's number gives us the number of moles. multiplying that by the molecular weight gives us the mass. from the periodic table we find the gram-molecular weight of u to be238 and of f to be19. so,  

u

f

6

will have a gram-molecular weight of 352g.

answer; talc and gypsum;