Half Life Question?

Question

Ok so here is my question



"The half-life of radium-222 is 38 seconds. How many grams of radium-222 remain in a 12 gram sample after 76 seconds? After 114 seconds? How many half-lives haave occured when 0.75 grams remain?"

Thanks, I will choose you as best answer

To startrekt

"why am I doing your homework?"

Because I have a 48% In science and I need a 70 or higher to pass so I thought I could get some answers off here. =-p Thanks everyone who replied and helped me

Answer 1

after 76 seconds (2 half lives), 3 grams remain

after 114 seconds (3 half lives) 1.5 grams remain

for .75 remaining, 4 half lives have passed

Answer 2

After 38 seconds, 1/2 remains, so 6 grams
After 76 seconds, 1/2 of that remains, so 3 grams
After 114 seconds, 1/2 of that remains, so 1.5 grams
After 152 seonds, 1/2 of that remains, so .75 grams.
Hence 4 half lives.

Answer 3

Grams=12(1/2)^(t/38) where t is in seconds. after 76 sec., 3 grams. 114 sec., 1.5 grams. .75 grams after 152 seconds, or 4 half-lives.

Answer 4

The original Half-Life takes place at a remote civilian and military laboratory called the Black Mesa Research Facility. During an experiment, researchers at Black Mesa accidentally cause a "resonance cascade" which rips open a portal to an alien world, Xen. Creatures from Xen flood into Black Mesa via the portal and start killing everyone in sight. The player takes on the role of Gordon Freeman, one of the research scientists who had been involved in the accident and who now must escape the facility. At the end of the game, a mysterious figure colloquially known as the G-Man extracts Gordon from Black Mesa and "offers" him employment. Gordon is subsequently put into stasis.[26] In Half-Life 2, the story resumes with the G-Man taking Freeman out of stasis and inserting him into a train en route to City 17 an indeterminate number of years after the Black Mesa incident. Official sources differ on the actual length of this intermission. A story fragment written by author Marc Laidlaw for the development team puts the intermission at ten years,[27] while Half-Life 2: Episode One's website puts this intermission as "nearly two decades" after the end of the events of Half-Life.[28] The environments in Half-Life 2, in accordance with the game's story, all have a distinct post-apocalyptic theme, yet in design they are varied, and include the Eastern European-styled City 17, the zombie-infested Ravenholm; the coastal Nova Prospekt prison and the massive Combine Citadel. Viktor Antonov, the art director of Half-Life 2, who spent his childhood in Bulgaria, wrote that the developers consciously modeled Half-Life 2's setting on Eastern Europe because they were fascinated by the region's combination of both new and old architecture and desired to infuse City 17 and its environs with the same sense of history.

Answer 5

12g=0s, 6g=38s, 3g=76s, 1.5g=114s, .75g=152s

76 seconds is 3 grams, 114 seconds is 1.5 grams, .57 grams is 152 seconds or 4 half lives.

why am I doing your homework?

Answer 6

the amt remaining is
M=Mo*2^-(t/38)
Mo=12 g
M(76)=12*2^-2=12/4=3 g
M(114)=12*2^-3=12/8=1.5 g

.75=12*2^-t/38
.75/12=2^-t/38
.0625=2^-t/38

0.0625=2^-4
-4=-t/38
4 half lives or 152 sec or 2 min 32 sec

Answer 7

I believe that 'Half- life' only refers to its radiation output not its mass.

Therefore after as much time as you like there will still be 12 gm.

However, after 4 'half-lives' only 6.25% of its original radiation will remain.

(Someone correct me if I'm wrong)

Answer 8

yupchagee's answer is the mathematically correct one. That's what half-life is all about.

Answer 9

wat is a half life???