Question

The elements P, Q and R are one of the Döbereiner's triad of elements in the increasing order of their atomic masses. If the atomic masses of P, Q and R are $x,y$ and $z$ respectively, then

• A. $x=2y+z$
• B. $z=x+y$
• C. $z=2x-y$
• D. $x+y+z=3y$

Answer 1

The correct option is D $x+y+z=3y$

According to Döbereiner's triad of elements , atomic mass of the middle element in the triad is the average of the atomic masses of the other two elements in the triad. Hence,

$y=\frac{x+z}{2}$
$\Rightarrow 2y=x+z$
Then,
$\Rightarrow x+y+z=3y$