-ecuatia reactiei
1mol 1mol
M+ 2H2O---> M(OH)2 +H2
A,g................................22,4l
6,85..............................1,12l ; am notat cu A masa molara a metalului
1,12xA=22,4x6,85------------> A=.................CALCULEAZA si cauta in tabel metalul aflat in grupa IIA care are aceasta masa molara....