To find the molar mass of ZnBr2, we first need to determine the molar mass of each element in the compound.

The molar mass of Zinc (Zn) = 65.38 g/mol
The molar mass of Bromine (Br) = 79.90 g/mol

Now, we can calculate the molar mass of ZnBr2:
Molar mass of ZnBr2 = 2(molar mass of Br) + molar mass of Zn
Molar mass of ZnBr2 = 2(79.90 g/mol) + 65.38 g/mol
Molar mass of ZnBr2 = 159.80 g/mol + 65.38 g/mol
Molar mass of ZnBr2 = 225.18 g/mol

Now, to find the mass of ZnBr2 in 81g of ZnBr2, we can use the formula:
Mass = Number of moles * Molar mass

Number of moles of ZnBr2 = mass / molar mass
Number of moles of ZnBr2 = 81g / 225.18 g/mol
Number of moles of ZnBr2 = 0.36 mol

Now, we can find the mass of ZnBr2 in 0.36 mol:
Mass = 0.36 mol * 225.18 g/mol
Mass = 81.06 g

Therefore, the mass of ZnBr2 in 81g of ZnBr2 is 81.06g.