Q34 of 149 Page 211

An element Z contains two naturally occurring isotopes . If the average atomic mass of this element be 35.5 u, calculate the percentage of two isotopes.

Given, Average atomic mass = 35.5 u

Let % amount of 35Z17 be y, then amount of 37Z17 is (100 - y).


So,



So, 35y + 3700 – 37y = 3550


Hence, y = 75


Thus, amount of 35Z17 is 75% and amount of 37Z17 is 25%


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