este vorba de HALOGENURA, ;notez X -halogenul care poate fi F, Cl, Br ,I
1mol......................1mol
KX + AgNO3---> AgX + KNO3
(39+A),,,,,,,,,,,,,,(108+A)
11,9....................18,8
18,8(39+A)= 11,9(108+A)=====> A= 80g/mol.................cauta in tabel halogenul care are masa molara gasita, 8og/mol