Is this supposed to be a question?????
MgBr2(aq) is an ionic compound which will have the releasing of 2 Br⁻ ions ions in water for every molecule of MgBr2 that dissolves.
MgBr2(s) --> Mg+(aq) + 2 Br⁻(aq)
[Br⁻] = 0.065 mol MgBr2/1L × 2 mol Br⁻ / 1 mol MgBr2 = 0.13 M
The answer to this question is [Br⁻] = 0.13 M
What they have in common is that they both have the same number of atoms.
The lack of a number preceding the carbon symbol C and the compound formula CO2 shows that there is one carbon atom and one carbon dioxide molecule. Subscript numbers in chemical formulas represent the number of atoms or molecules immediately preceding the subscript.
Majority of the atoms mass is found in the nucleus, which consists of protons and neutrons. Neutrons have a neutral charge, while protons have a positive charge.