chem doubt

A compound contains 28% N and 72% of a metal by weight.3 atoms of metal combine with 2 atoms of N.Find the atomic weight of metal:

a)38
b)30
c)24
d)18

5 Answers

is the answer (a)

sorry i wrote the atomic mass of whole compound the answer is (c)

Please tell me how did you get the answer.

look 3 atom of metal combine with 2 of nitrogen so empirical formula of compound is N₂M₃ .

using empirical formula calculations

N - 28/14 =2
M - 72/M1 (M1 = atomic mass of M)

but the empirical formula is 2:3
therefore

2/3= 2/(72/M1)
M1 = 24

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