Final answer:
The formula mass of strontium bromite, Sr(BrO₂)₂, is calculated by adding the atomic masses of strontium, bromine, and oxygen. Each bromite ion contributes one bromine atom and two oxygen atoms to the formula unit. The total formula mass is 311.428 amu.
Step-by-step explanation:
To calculate the formula mass of strontium bromite, Sr(BrO₂)₂, we will add the atomic masses of all the atoms present in one formula unit of the compound.
The atomic mass of strontium (Sr) is 87.62 amu, and the average atomic mass of bromine (Br) based on the isotopes 79Br and 81Br is approximately 79.904 amu. The atomic mass of oxygen (O) is 16.00 amu.
Each bromite ion (BrO₂)⁻ contains one Br atom and two O atoms.
So for one strontium bromite formula unit, we have:
1 Sr atom = 87.62 amu
2 Br atoms (in 2 BrO₂)⁻ = 2 × 79.904 amu
= 159.808 amu
4 O atoms (in 2 BrO₂)⁻ = 4 × 16.00 amu
= 64.00 amu
Add these together to get the formula mass:
87.62 amu (Sr) + 159.808 amu (2 × Br) + 64.00 amu (4 × O) = 311.428 amu
Therefore, the formula mass of strontium bromite, Sr(BrO₂)₂, is 311.428 amu.