Statement-1: If an element X consists of two isotopes, X A 1 and X A 2 , and their average atomic mass is A a vg , then the percentage abundance of X A 1 is given by ( A 1 − A 2 ) ( A a vg

Question

Statement-1: If an element X consists of two isotopes, $X^{A_{1}}$ and $X^{A_{2}}$ , and their average atomic mass is $A_{a vg}$ , then the percentage abundance of $X^{A_{1}}$ is given by $\frac{( A _{a vg} - A _{2} )}{( A _{1} - A _{2} )} \times 100$ .

Statement-2: The average molar mass of a gaseous mixture containing equal masses of $CH_{4}$ and $SO_{2}$ is $32 g mol^{- 1}$ .

TestHub · Accepted Answer

Statement-1: Let x be the fractional abundance of X A 1 ​ . Then A a vg ​ = A 1 ​ x + A 2 ​ ( 1 − x ) . Solving for x : A a vg ​ − A 2 ​ = x ( A 1 ​ − A 2 ​ ) , so x = ( A 1 ​ − A 2 ​ ) ( A a vg ​ − A 2 ​ ) ​ . Percentage abundance is x × 100 . Statement-1 is TRUE. Statement-2: Let mass of each gas be m . Moles of CH₄ = m /16 . Moles of SO₂ = m /64 . Total moles = m /16 + m /64 = 5 m /64 . Total mass = 2 m . Average molar mass = 5 m /64 2 m ​ = 5 128 ​ = 25.6 g m o l − 1 . Statement-2 is FALSE. Therefore, Statement-1 is true and Statement-2 is false.

Chemistry - Mole Concept Question with Solution | TestHub

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JEE Main 2028 (Class 11)