Write the number of neutrons present in C and C isotopes of carbon

CBSE Class 9 CBSE Class 9 Science
1
  1. Given that natural sample of iron has isotopes image in the ratio 5%, 90% and 5% respectively. What will be the average atomic mass of Fe? Write any two applications of isotopes.
    • The relative atomic mass of boron is 10.8. Calculate the percentage of its isotopes image occurring in nature.
    • Write the number of neutrons present in C and C isotopes of carbon.
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  1. Average atomic mass of Fe = image = image = image = 55.95 u
    Two applications of isotopes are
    • C-14 is used to determine the age of old samples of fossils.
    • Co-60 is used in the treatment of cancer (radiotherpy).
    • Let the percentage of image be Y in the sample and the percentage of image will be (100 - Y) .
      Average mass = image
      10Y + 11(100 - Y) = 1.08 x 100
      10Y + 1100 - 11Y = 108
      ⇒ Y = 20
      Therefore, the percentage of image = 20% and percentage of image = 100 - 20 = 80%.
    • Number of neutron in image = Mass number - atomic number = 12 - 6
      Number of neutrons in image = 14 - 6 = 8