Posted by **Sally** on Monday, January 28, 2013 at 10:26am.

how many half lives have passed if only 0.625g remain of the original 40g?

- Chemistry -
**Steve**, Monday, January 28, 2013 at 10:54am
(1/2)^n = .625

n ln(1/2) = ln(.625)

n = .678

makes sense, since one full half-life leave 1/2, which is a bit less than .625

- Chemistry -
**DrBob222**, Monday, January 28, 2013 at 3:28pm
This answer of 0.678 makes no sense to me. By iteration you know that if the sample starts at 40 and ends up at 0.625 it must have gone through six half-lives. Mathematically it is done this way.

2^n = 40/0.625 = 64

n*log 2 = log 64

0.301n = 1.8062

n = 1.8062/0.301 = 6.0

## Answer this Question

## Related Questions

- science - how many half-lives have passed if only 1/16 of the original amount of...
- chemistry - what fraction of an original sample of a radioactive isotope remains...
- Chemistry - Which radioactive sample would contain the greatest remaining mass ...
- Chemistry - How many half-lives have passed if 87.5% of a substance has ...
- chemistry - how many half-lives of radon-222 have passed in 11.46 days?
- Chemistry - If a 100.0 gram sample of a radioactive isotope goes through three ...
- Chemistry - K-42 has a half-life of 12.4 hours. If you begin with 250g of K-42, ...
- chemistry - the half-life of polonium-218 is 3.0 minutes. what percentage of the...
- chemistry - Find the number of disintegrations per minute emitted by 1.1 mol of...
- Science - if the wood in the bowl contains only 1/16 of its original C-14, then ...