Germanium -66 has a half-life of 2.5 hours. you have 35 grams of radioactive material. after 16 days, how much radioactive material remains?

Hey there!

A half-life means after a certain amount of time, half of that substance will be gone/changed after that time.

How many half-lives are in 16 days?

Multiply 16 by 24 (to get the total hours) and divide that by 2.5.

That is 153.6 half-lives.

35(0.5)^(153.6) represents the equation for this.

Simplify this and get 8.88 x 10^(-45).

There will be 2.02 x 10^(-45)g of germanium-66 sample remaining after 16 days.

Hope this helps!

n2(g) + 3h2-> 2nh3(g)   this is the balanced equation

note the mole ratio between n2, h2 and nh3.   it is 1 : 3 : 2   this will be important.

moles n2 present = 28.0 g n2 x 1 mole n2/28 g = 1 mole n2 present

moles h2 present = 25.0 g h2 x 1 mole h2/2 g = 12.5 moles h2 present

based on mole ratio, n2 is limiting in this situation because there is more than enough h2 but not enough n2.

moles nh3 that can be produced = 1 mole n2 x 2 moles nh3/mole n2 = 2 moles nh3 can be produced

grams of nh3 that can be produced = 2 moles nh3 x 17 g/mole = 34 grams of nh3 can be produced

note:   the key to this problem is recognizing that n2 is limiting, and therefore limits how much nh3 can be produced.

that's what i got you can count the number of atoms