Monday

March 30, 2015

March 30, 2015

Posted by **amanda** on Friday, October 31, 2008 at 7:07pm.

b)how much of a 3.50-mg smaple of nickel-63 will remain after 368 years? the half-life of nickel-63 is 92 years?

- chemistry -
**DrBob222**, Friday, October 31, 2008 at 8:11pmThere is a short way and a long way of doing these. The short way is easy if the numbers are right. In this case they are.

a) Note that 13.5/4.5 = 3.00 half lives; therefore, 1/2 of 12.0 mg sample = 6.0 mg left after the first half life, 1/2 of that = 3.0 mg left after the 2nd half life and 1/2 of that = 1.5 mg left after the 3rd half life.

b) This is done the same way if you notice that 368 years/92 years = 4.00 half lives.

Here is the long way of doing them when the number of half lives is not an even number.

k = 0.693/t_{1/2}

ln(No/N) = kt

So, for the first one,

k = 0.693/t_{1/2}

k = 0.693/4.5 = 0.154

Then substitute into the other equation for k you've just calculated.

ln((No/N) = kt

ln(12.0/N) = 0.154*13.5

ln(12.0/N) = 2.079

Take the antilog of both sides.

12.0/N = 8.0

N = 12.0/8.0 = 1.5 mg

The b part is done the same way the long way, too.

N=12.0/1.053 =

**Answer this Question**

**Related Questions**

Chemistry - indium-115 has a half life of 4.5 hours, if you start with a 12.0mg ...

math - The radioactive isotope sodium-24 is used as a tracer to measure the rate...

physics - The half-life of a certain radioactive isotope is 32 hours.What ...

Chemistry - The half-life of xe-133 is 126 hours. Starting with 250 mg, after ...

Chemistry-help please! - The half-life of Xe-133 is 126 hours. Starting with 250...

MATH - solving exponential equations - The half-life of sodium-24 is 14.9 hours...

science - A half-life of mercury-195 is 31 hours. If you start with a sample of ...

Chemistry - Potassium-42 has a half life of 12.4 hours. How much of an 848 g ...

physical science - sodium-24 has a half life of 15 hours,how much of a 50 gram ...

Chemistry - I've figured out most of it. I'm not sure how to find the percentage...