`#huy`
a) `M + Cl_2 -> MCl_2`
`MM = 1,2/(MM) mol`
`MMCl_2 = 4,72/(MM + 71) mol`
tỉ lệ `mol 1 : 1`
`=> MM = MMCl_2`
`<=> 1,2/(MM) = 4,72/(MM + 71)`
`<=> 4,72/(MM) = 1,2(MM+ 71)`
`<=> 4,72/(MM) = 1,2MM + 85,2`
`<=> 3,52/(MM) = 85,2`
`<=> MM = 24 (Mg)`
vậy `M` là `Magie : Mg`
`b)nMg = 1,2/24 = 0,05 mol`
`=> mMgCl_2 = 0,05.95 = 4,75g`