Answer:
The decreasing order of masses of for different BrCl molecules :
= 
= 
Explanation:
The two naturally occurring isotopes of bromine are
81-Br (80.916 amu, 49.31%)
79-Br (78.918 amu, 50.69%).
The two naturally occurring isotopes of chlorine are
37-Cl (36.966 amu, 24.23%) and
35- Cl (34.969 amu, 75.77%).
Molar mass of BrCl molecule composed of 81-Br and 37-Cl.
Mass of 81-Br = 80.916 amu
Mass of 37-Cl = 36.966 amu
Molar mass of this BrCl molecule,
= 80.916 amu + 36.966 amu
= 117.882 amu
Molar mass of BrCl molecule composed of 79-Br and 35-Cl.
Mass of 79-Br = 78.918 amu
Mass of 35-Cl = 34.969 amu
Molar mass of this BrCl molecule
= 78.918 amu + 34.969 amu
= 113.887 amu
Molar mass of BrCl molecule composed of 81-Br and 35-Cl.
Mass of 81-Br = 80.916 amu
Mass of 35-Cl = 34.969 amu
Molar mass of this BrCl molecule,
= 80.916 amu + 34.969 amu
= 115.885 amu
Molar mass of BrCl molecule composed of 79-Br and 37-Cl.
Mass of 79-Br = 78.918 amu
Mass of 37-Cl = 36.966 amu
Molar mass of this BrCl molecule,
= 78.918 amu + 36.966 amu
= 115.884 amu
The decreasing order of masses of for different BrCl molecules :
=
= 
