Usually concentrations are expressed as molarity, or moles of solute per liter solution. First, convert the mass of bromide ion to moles. The molar mass of bromine is 79.904 g/mol.
Moles of bromine = 65 mg * 1 g/1000 mg * 1 mol/79.904 g = 8.135×10⁻⁴ moles
Next, convert the mass of seawater to volume using the density.
Volume of seawater = 1 kg * 1 m³/ 1,025 kg * 1000 L/1 m³ = 0.976 L
Thus,
Molarity = 8.135×10⁻⁴ moles/0.976 L = 8.335×10⁻⁴ M
