If a half life is 2.5 hours, how long is 2 half life's

Im not really sure what a half life is, but two of them would be 5.0 hours

5 hours

Explanation:

cause if half life is 2.5hours we just multiply it by two and get 5 hours

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.