chem
posted by Margaret .
Can someone please help me with the following questions?
1:Suppose you were given an ancient wooden box. If you analyze the box for carbon14 activity and find that it is 50% of that of a new piece of wood of the same size, how old is the wood in the box?
2:How old is an Egyptian scroll made of papyrus that contains 75% of the amount of C14 that would be found in a piece of paper today?
Please and thank you!
1. The halflife of a material is the time it takes for 1/2 of the material to disintegrate. Thus, the box, if it has lost 50% of its activity, must have gone through one halflife. What is the halflife of C14? Take 1/2 of that.
2. Suppose you start with 100 atoms of C14. If the activity is now 75%, we must have 75 atoms today.
ln(No/N)=kt
No=100
N=75
k=0.693/t_{1/2}
Substitute the halflife for t_{1/2} to find k, then substitute k into the ln equation and solve for t.
Post your work if you get stuck and need further assistance.
1) The halflife of C14 is 5730, so would the answer be 2865 years?
2)Is this how I should do it?
In(100/75)=.693/t1/2
But how do I do it when you said it's k*t and .693/t1/2 is .693 divided by t
2865 years is right.
For #2.
k= 0.693/5730 = ?? (plug in below).
ln(100/75)=k*t =
ln(100/75)=??*t
Solve for t.
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