Question

Hi, can some one please help me :)

Iodine-131 has a half-life of 8 days. In how many days will a 1 kg sample of iodine-131 decay and reduce to 0.0625 kg of iodine-131?

8 days

16 days

24 days

32 days

Answer 1

do u think u know this @JFraser

Answer 2

half-life always means the same percentage of a radioactive substance will decay over that given period of time. In order for 1000g of I-131 to decay to 62.5g of I-131, you have to find out what percentage remains, and what percentage has decayed.

What percentage of 1000g is 62.5g?

Answer 3

Or, you can think of it this way:

How many times can you cut 1000g in half before you get to 62.5g?

Answer 4

okay , let me try to figure this out

Answer 5

oh, the answer is 16 thanks so much for the help!, i am giving u a medal. If you dont mind can u help me with another one?

Answer 6

the answer is not 16 days

Answer 7

its not?

Answer 8

each half life is 8 days. after each half life, the amount of I131 remaining will be cut in half. So...

Answer 9

oh 4

Answer 10

lol

Answer 11

WAIT!

Answer 12

THERE IS NO 4 I AM CONFUSED!

Answer 13

0 days: 0 half-lives: 1000g left
8 days: 1 half-life: 500g left (500g decayed)
16 days: 2 half-lives: 250g left (750g decayed)
...
keep going dividing the mass

Answer 14

it's 4 HALF-LIFES, but each half-life takes 8 days

Answer 15

oh, so 32 correct?

Answer 16

lol i suck at science..good at everything else just not science :(

Answer 17

but if you feel like it, can u help me with anther one, it is sort of like this

Answer 18

One scientist kept 20 grams of a radioactive material in a container. What will be the mass of the radioactive material left in the container after 2 half lives?

4 grams

5 grams <<<<--------

10 grams

40 grams

that is what i think

Answer 19

@JFraser

Answer 20

looks right to me

Answer 21

thanks man, is there anyway i can give u 2 medals lol?

Answer 22

instead of asking several questions in the same post, close the one and open a new one

Answer 23

okay i will thanks :)