Chlorine occurs in nature in two isotopic forms with masses 35 u and 37 u

CBSE Class 9 CBSE Class 9 Science
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1

(i) Chlorine occurs in nature in two isotopic forms with masses 35 u and 37 u. The percentage of 35 Cl is 75%. Find the average atomic mass of chlorine atom.
(ii) Give any three applications of isotopes.

2

(i) % of ${}^{37}Br$= 100-75 = 25%
Average atomic mass = (35 x 75/100 + 37 x 25/100) = 105 + 37 /4 = 142/4 = 35.50
(ii) Applications of isotopes
(a) An isotope of iodine (I-131) is used in the treatment of goitre.
(b) P-32 is used in agricultural research.
© Na-24 is used to detect blood clots.