Chemistry

How many half-lives have passed if 87.5% of a substance has decomposed? How many if 99.999% has decomposed?

For 87.5% decomposition 1/8 is left.
(1/8) = (1/2)^3
Three half lives is the answer

Fot 99.999% decomposition, 10^-5 is left.
Solve 10^-5 = (1/2)^n for the number of half-lives, n. Take the log of each side of the equatiuon for a quick solution.

  1. 👍 0
  2. 👎 0
  3. 👁 338
asked by John

Respond to this Question

First Name

Your Response

Similar Questions

  1. science

    how many half-lives have passed if 87.5% of a substance has decomposed? how many if 99.999% has decomposed?

    asked by Kim on March 14, 2011
  2. math

    The half life of the radio active substance is the time require the half the substance to decay. the mount A ( in grams) of 100 gram sample of a radio active substance remaining after t half lives by A equals to 100 (0.5) t.

    asked by sai on January 17, 2018
  3. science

    Using absolute dating,a fossil is dated to be 3 million years old and decomposed 1 half-life. If it takes the same fossil 12 million years to decompose to 4 half-lives,how old will the fossil be when it is measured to be at

    asked by Cherie on May 25, 2012
  4. Science

    If the initial amount of Carbon-14 in the mammoth was 8 grams, how many half-lives have passed i the fossil sample has 1 gram left? How many years have passed since the mammoth's death?

    asked by Anonymous on November 2, 2017
  5. chemistry

    how many half-lives of radon-222 have passed in 11.46 days?

    asked by Jerry on May 23, 2011
  6. algebra

    1) how many billions of years will it take 1000 grams of uranium-238 to decay to just 125 grams? 2) a researcher had 37.5 g left from a 600 g sample of sulfer-35. how many half-lives passed during that time? 3) look at problem 2.

    asked by anon on May 9, 2013
  7. Chemistry

    how many half lives have passed if only 0.625g remain of the original 40g?

    asked by Sally on January 28, 2013
  8. science

    how many half-lives have passed if only 1/16 of the original amount of the element remains? a-two b-three c-four d-five

    asked by Anonymous on September 28, 2011
  9. chemistry

    what fraction of an original sample of a radioactive isotope remains after three half-lives have passed? 1/8?

    asked by jake on October 13, 2012
  10. Calculus

    Write the recurring decimal 0.abcabcabc… as a fraction. a) (a+b+c)/999 b) (100a+10b+c)/999 c) (abc)/999 --> I did this but my teacher said I was wrong d) (100c+10b+a)/999

    asked by Alice on April 11, 2019

More Similar Questions