Question

if only 12.5% Mo remains after 200 hours, show that its half life is 66.7 hrs

Answer 1

hey

Answer 2

hello

Answer 3

ok its me so what is the question again cuz I handed in the wkst but I have the problem done

Answer 4

the mummy one?

Answer 5

your choice

Answer 6

both? haha im really bad at chem

Answer 7

ok we'll start with the one you just posted

Answer 8

ok

Answer 9

so we are going label Ao= 1 because its 100% A= 12.5% or .125

Answer 10

we have to solve for k first and we also know t=200

Answer 11

now use the equation \[A =A_oe^(-kt)\]

Answer 12

are ewe using A= Aoe -kt equation

Answer 13

yeah

Answer 14

ok

Answer 15

just plug in the numbers and write equation not doing any math

Answer 16

now it take the ln.125=lne-k200 lne goes away so its just ln.125=-k200

Answer 17

there isn't a negative sorry

Answer 18

on the k200?

Answer 19

with the last thing I said

Answer 20

yeah

Answer 21

ok...got that

Answer 22

i have.... ln.125=k200

Answer 23

what do you have now

Answer 24

now divideln.125 by 200

Answer 25

-.01039

Answer 26

did you divide with a neg

Answer 27

no....i did ln(.125) then i divided it by 200

Answer 28

then you were suppose to keep the negative haha

Answer 29

ok that makes sense

Answer 30

then you have to use the half life equation ln2/k which is the value you just found to get the half life

Answer 31

woah...i got it!

Answer 32

yay!!!!!

Answer 33

now if i can remember it for the test hah

Answer 34

except you have to find 200hrs

Answer 35

and you just work backwards

Answer 36

are you ready for the mummy question

Answer 37

what...no i dont it says show that he half like is 66.7 hrs and thats what i just did

Answer 38

ohhh on the test you mean?

Answer 39

should i just write it here or post it as a new question?

Answer 40

yeah that's for the test and just write the question here

Answer 41

a mummy is found to be 3940 years old by C dating. Using a half life of 5730 years for C, demonstrate that 62.1% of the C at the death of the person remains in his mummy

Answer 42

ok so use the half life equation with ln2/t(1/2) =k

Answer 43

what is the equation before math

Answer 44

\[Ao \div 2= Aoe -kt1/2\]

Answer 45

no use ln2/t t=the half life time

Answer 46

the ln2=kt1/2

Answer 47

no ln2/t=k

Answer 48

you need to find k before anything

Answer 49

isnt it ln2/t1/2=k

Answer 50

yeah

Answer 51

I didn't want to confuse by adding the 1/2

Answer 52

okay

Answer 53

so now what is t1/2

Answer 54

5730 years

Answer 55

yeah so solve for k now

Answer 56

1.209x10^-4

Answer 57

good now use the A=Aoe^-kt Ao=100% or 1and we know k and t is the other time now

Answer 58

and were solving for A?

Answer 59

yeah

Answer 60

use the e to the powet button

Answer 61

then whats the 62.1%

Answer 62

oh is that A, hahah

Answer 63

A=e^-.4766 -----> A=.621 or 62.1%

Answer 64

yea haha

Answer 65

i got 50.01%

Answer 66

did you get e^-.4766

Answer 67

no mine was e^-.6927

Answer 68

you multiplied (1.21x10^-4)x3940

Answer 69

oh nno...i used 5730...oops

Answer 70

yeah you have to go back to the other time

Answer 71

ok lemme recheck

Answer 72

ok got it...now is that how its worded on the test

Answer 73

ok I just did it and I got it

Answer 74

yeah that one is the same

Answer 75

ok..and are the nuclear equations the same or does he change those

Answer 76

there are some of the same and som enew ones

Answer 77

I have to go do you have any last questions

Answer 78

ok and the quarterly is all the same justt in multiple choice form?

Answer 79

hyeah exactly the same

Answer 80

ok thank you so much!!