Question

Atomic mass of X and Z are 20 and 40 respectively. If X, Y and Z are in Dobereiner’s triads, what should be the atomic mass of Y?

• A. 20
• B. 40
• C. 30
• D. 60

Answer 1

The correct option is C

30

Since, Y is the middle element of the triad, its mass should be the average of 20 and 40, i.e. 30.