I need help with questions 10, 11, and 12 please. I\'m including all of the data

Question

I need help with questions 10, 11, and 12 please. I'm including all of the data for the lab, however, I dont think it is needed for this question. If possible, please show the steps for how you arrived at your answer, Once again, I ONLY need the anwer to questions 10, 11, and 12, which I attempted but I'm pretty sure its wrong..Thanx. Number ten is at the bottom of the page; its the M&M question, Number 11 and 12 are are the first page,only they look like they say number 1 and 2, because they got cut off when I scanned them.

Report sheet Exp. 12 Radioactivity Lab Section Date ame: 1) How might the apparent "age" of the sample in question #10 be affected if more pinto beans an be added? 2 Potssium-40 (Half Life 1.4 x 109 yrs decays by K-capture to argon-40. Calculate the age of moon rock if it was found to contain 18% potassium and 82% argon by mass. 40 K orde rata case 3 of doc n Z ln(r) o, G93

Explanation / Answer

12)   

Radio active decay is a first order reaction.

For first order recation,

half life t1/2 = 0.693 /k where k is rate constant

k = 0.693/ t1/2 --- Eq (1)

k = 1/t ln{ [A]o/[A]t} -----Eq (2)

From Eqs (1) and (2),

0.693/ t1/2 = (1/t) ln {[A]o/ [A]t} ------Eq (3)

t =age of the moon rock

Given that

t1/2 = 1.4 x 109 yrs

Initial amount of potassium [A]o = 100 %

Final amount of potassium [A]t = 18%

Substitute all the values in Eq (3),

0.693/ t1/2 = (1/t) ln {[A]o/ [A]t}

0.693/ 1.4 x 109 yrs = (1/t) In (100/18)

t = [In (100/18)] x 1.4 x 109 yrs / 0.693

= 3.5 x 109 yrs

t = 3.5 x 109 yrs

Therefore,

age of the moon rock = 3.5 x 109 yrs

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.