Answer:
OK!!.
N=N(½)ⁿ
n= Time/half life
N=Remaining Mass
N°=Initial Mass or Mass before decay.
t= time taken to decay(Its in Months in this case)
t½= Half Life of the Material. This is the time taken to decay to half its initial value.
N°= 2000mg
a).Equation that Models this is
since n=t/t½
N=N°(½)ⁿ =
N=N°(½)^t/t¹'². This should be your answer.
b). We're asked to find the remaining mass of substance in 4years.
t= 4years
Our Half life is in Months... So we gotta convert or time t from year to Months too.
4yrs === 4x12 = 48Months.
N° was given as 2000mg
N=N°(½)^t/t½
N= 2000(½)^48/3
N=2000(½)^16
Using your calc to evaluate (½)^16... Then multiply by 2000
N=0.0305mg will remain after 4years.
Or After 16Half Lives since 1 half life is 3months
c). We're looking for t this time
N=N°(½)^t/t½
Since it asked for 750mg to remain ... 750 is now our N --- Remaining Mass
750 = 2000(½)t/3
To Isolate "t" and make it the subject
750/2000 = (½)^t/3
0.375 = (½)^t/3
Taking ln(natural log) of both sides
Ln(0.375) = Ln(0.5)^t/3
From the rule of logarithm...
You can bring the power (I.e t/3) to the front
You'll have
Ln(0.375) = t/3Ln(0.5)
Dividing both sides by Ln(0.5) to isolate t
Ln(0.375)/Ln(0.5) = t/3
t/3 = 1.415
t= 3x1.415
t=4.25months.
Have a great day.
Hope this helps... I'm open to questions if you have any too.
