please help! i dont understand this.
a 25 gram sample substance that's used for drug research has a k-value of 0.1229. find the substances half-life, in days using the exponential decay formula. round your answer to the nearest tenth

Respuesta :

instead of using 0.41No you use 0.5No. rearranging the same way gives you t=(ln0.5)/(-k)=5.5 to the nearest 10th

Answer:

Half life period = 43.11 days

Step-by-step explanation:

A sample substance has been taken for the use of drug research.

Weight of the substance taken = 0.25 gram

We have to use the formula of exponential decay to find the half life period of the substance.

Formula for the decay is [tex]A_{t}=A_{0}e^{-kt}[/tex]

Where [tex]A_{0}[/tex] is the weight of the substance taken initially

[tex]A_{t}[/tex] is the quantity remained after t time

and t = time

Now we have to find the half life life period

[tex]A_{t}[/tex] = [tex]\frac{0.25}{2}=.0125[/tex]

and [tex]A_{0}=25[/tex]

By putting these values in the formula

0.125 = 25[tex]e^{-0.1229t}[/tex]

[tex]e^{-0.1229t}[/tex] = [tex]\frac{0.125}{25}[/tex]

[tex]e^{-0.1229t}[/tex] = 0.005

Now we take natural log on both the sides of the equation

[tex]ln(e^{-0.1229t})=ln(.005)[/tex]

-0.1229t(lne) = -5.2983

0.1229t = 5.2983

t = [tex]\frac{5.2983}{0.1229}=43.11 days[/tex]≈ 43.10 days

Therefore, half life period of the substance is 43.10 days