### question on CALM topic 19, Section 1, question 9

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Hi,

I was wondering if anyone could give me any hints on how to solve for question 9 in chapter 19, section 1. The problem ID is 955133119. Thanks!

-- Anonymous, April 07, 2000

are you sure that section i of chpt 19 has a problem number 9???????

-- Anonymous, April 07, 2000

Sorry, you're right, Tara. I meant chap 15, not 19. Please give me a hint. I think you are also having trouble with this one, too? thanks

-- Anonymous, April 07, 2000

since this problem is like problem number five, i can not gve you any hints becuase i don't know how to do #5. If i did I would help out.

-- Anonymous, April 07, 2000

Thanks Tara, I appreciate it, but I meant one of the TA, if it is possible for them to help us before 5 PM would be wonderful. If not, eh, just extra credit, right?

-- Anonymous, April 07, 2000

how did you do numeber five.

-- Anonymous, April 07, 2000

You know what, Tara? I checked on prob 5, and I have absolutely NO IDEA how I did that one. I got credit, though, which is probably indicative that I did do it at some point, probably when the problems were just assigned. Sorry.

-- Anonymous, April 07, 2000

use the equation: ln(N/Ni) = -(.693/half life)t

N = # of atoms after the substance has decomposed Ni = # of atoms at time=0 t = time it took for the substance to decompose

Solve for half life and this should work.

*Note: for problems that deal with concentrations, NOT atoms, use the first order integrated rate law to find k, then, since

ln(N/Ni) = -(.693/half life)t = -kt

subsitute your value of k in here and solve -(.693/half life)t = -kt for the half life

Hopefully, this will help....

-- Anonymous, April 07, 2000

thanks, i really appreciate this.

-- Anonymous, April 07, 2000

Thank you so much, Erin! You helped me so much! I did the problem and got it right! Thanks again.

-- Anonymous, April 07, 2000