Question
Mon July 25, 2011 By: Sunarmik Das
 

12g of alkaline earth metal gives 14.8g of its nitride . Atomic weight of metal is?

Expert Reply
Mon July 25, 2011

Let M is the alkaline metal with atomic weight = X u

Therefore  3M2+ + 2N3- 

So, 3 moles of M2+ gives 1 moles of

or, 3X gm of M2+ gives (3X +28) gm of

or, 1 gm of M2+ gives
or ,12 gm of M2+ gives 
But   12 gm of M2+ gives  14.8 gm of nitride.
 
Therefore
 
or,   3X + 28 = 3.7X

       X = 40 u

Therefore, the atomic weight of metal is 40 u.

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