Question

PLEASE HELP ME!! pleaseeeee

Answer 1

`P_2 O_5`has molar mass of 142 g.

Explanation:

Firstly we will find out the atomic weight of the elements of the compound.

Mg = 24 P = 31 Al = 27 Cl = 35 Ba = 137 O = 16

Now 1st compound is
`Mg Cl_2`, in this compound there is 1 atom of Magnesium and 2 atom of Chlorine.

So atomic weight of
`Mg Cl_2`=
`24+2*35=24+70=94`

2nd compound is
`P_2 O_5`, in this compound there is 2 atom of Phosphorus and 5 atom of Oxygen.

So atomic weight of
`P_2 O_5` =
`2*31+5*16=62+80=142`.

3rd compound is
`Ba Cl_2`, in this compound there is 1 atom of Barium and 2 atom of Chlorine.

So atomic weight of
`Ba Cl_2`=
`137+2*35=137+70=207`

4th compound is
`Al Cl_3`, in this compound there is 1 atom of Aluminium and 3 atom of Chlorine.

So atomic weight of
`Al Cl_3`=
`27+3*35=27+105=132`

Hence the substance having molar mass of 142 g is
`P_2 O_5`.