To Drbob222

I don't get how to get N, please show me cause I don't understand

  1. 👍 0
  2. 👎 0
  3. 👁 132
  1. You follow the math.
    k = 0.693/t1/2
    Then
    ln(No/N) = kt
    No = 120 ug
    N = solve for this
    k = from above
    t = 120 sec.

    First, you substitute the half life of this material which is listed as 20 seconds and that allows you to solve for k. You need k to solve the equation below it in the solution above.
    Then you substitute 120 ug for No (No is what you have at the beginning). N is what you have at the end and that is what you're solving for. N is the only unknown in the equation. Then substitute k from the first calculation above. t in the problem is 2 minutes but since the half life was given in seconds this 2 min need to be convert to seconds which is 120 s. So the final equation looks like this
    ln(120/N) = k(120). I don't remember k but that is what you obtained from above. Solve for N.

    1. 👍 0
    2. 👎 0
  2. Um so is it like this :
    0.693 x 120 = 83.16
    120/n=83.16
    =9979.2?

    1. 👍 0
    2. 👎 0
  3. No, you aren't following the math.
    The half life is 20 seconds.
    k = 0.693/t1/2 = 0.693/20 = 0.03465.
    Then ln(120 ug/N) = 0.03465*120
    Solve for N.
    By the way, that ln (which you don't have anywhere in your work) in front of the (No/N) is not for looks. That means to take the natural log (that's the log base e) of No/N.

    1. 👍 0
    2. 👎 0
  4. Alright, my final answer is 166.32
    is this correct?

    1. 👍 0
    2. 👎 0
  5. No. If the sample starts out at 125 ug and it loses half of the sample every 20 seconds, how can it have more than it started with at the end of 2 minutes. It MUST be less than 125 ug.

    1. 👍 0
    2. 👎 0
  6. Yah that's wut I thought so I tried again and I know I sound but is it .0115 ?

    1. 👍 0
    2. 👎 0
  7. K this was my equation 120in/n=1.386
    How do I solve for n?

    1. 👍 0
    2. 👎 0
  8. Much closer but not quite.
    I think part of the problem is the 1.386. I think that should be 4.158.
    k = 0.693/20 = 0.03465
    ln(125/N) = 0.3465*120
    ln(125/N) = 4.158
    Take the antilog of both sides.
    antilog ln(125/N) = 125/N
    antilog 4.158 = 63.94
    So 125/N = 63.94
    and N = 125/63.94 = 1.95 ug

    1. 👍 0
    2. 👎 0
  9. Oh now I get it! Thank u so much for ur help:)

    1. 👍 0
    2. 👎 0

Respond to this Question

First Name

Your Response

Similar Questions

  1. APChem

    Hi I tried to understand this but I don't know why the answer is B: Which one of the following pairs cannot be mixed together to form a buffer solution: A) NaC2H3O2, HCl B)RbOH, HBr C) NH3, NH4Cl D) H3PO4, KH2PO4 E) KOH, HF The

  2. Math

    Find the values of the variables. [-12 -w^2] = [2k -81 2f 3 -14 3 Please help me. I don't know how to do this at all, and can you show your work so I can understand better. Thanks

  3. physics

    two point charges are 10.0 cm apart and have chargeso of 2.0 uC (micro)and -2 uC, respectively. What is the magnitude of the electric field at the midpoint between the two charges? i think the answr is zero.. but i don't

  4. Math

    M is the set of integers that are greater than -1 and less than 4 I don't understand?? i know it's easy but i don't understand how to solve it

  1. surface area and volume

    I really need some help, I don't fully understand. Exspecially with fractions, don't know how to enter them on calculator. 1. What is the approximate volume of the sphere? 524 m³ (my choice) 1,000 m³ 1,256 m³ 1,570 m³ 2. What

  2. GENERAL CHEMISTRY

    CALCULATE THE pH AND HYDROLYSIS IN 0.10 M AlCl3 SOLUTION.Ka = 1.2 X 10-5 FOR [Al(OH2)6]+3,OFTEN ABBREVIATED Al+3.TELL WHETHER pH IS ACID OR BASE.GIVE IONIC EQUATION. Help us a little by telling us how much you know to do and

  3. Math

    A positive integer n is defined as a "prime interlude" if n-1 and n+1 are both prime numbers. Which of the following is not a "prime interlude?" a.4 b.18 c.30 d.72 e.90 ( First of all; What is a "prime interlude??") I don't

  4. Chemistry

    What is wrong with or ambiguous about the phrase "four molecules of NaCl" I really don't understand my textbook says in the back that it is an ionic compound so I guess that its not really a molecule then I don't understand...

  1. history

    I don't understand this question: the removal of general mcclellan represents a loss of the army and the potomac and a victory for the interfering politicans in washington (validate) i know that mcclellan was replaced by grant

  2. Math

    I am taking the Using Tables, Rules, and Graphs quiz part 2, and I dont understand these two problems. 1. Use the function rule to complete the table: -10x+y=y Above it shows a graph, with x and y marked, then along the top it

  3. Ms. Sue Help me please!

    Mrs. Miller sells a house for $179,000. If she earns a commission of 6%, how much money does she earn? Write a porportion and show your work. I don't understand how to do it, I have seen the other questions and I don't get how you

  4. ap history

    what was john walthall alleged offense?how might one account for the ferocity of the assault on carter's family walthall? I believe he sleeps with white women but i don't know what he stole. I don't understand the second question.

You can view more similar questions or ask a new question.