Answer:
12 moles Cl⁻
Explanation:
To find the moles Cl⁻, you need to (1) calculate the moles of magnesium chloride (MgCl₂) using the molarity equation and then (2) convert moles MgCl₂ to moles Cl⁻ (via the mole-to-mole ratio from formula subscripts). It is important to arrange the conversions in a way that allows for the cancellation of units.
Molarity (M) = moles / volume (L)
2 M = moles / 3 L
6 = moles MgCl₂
1 MgCl₂ = 1 Mg²⁺ and 2 Cl⁻
6 moles MgCl₂ 2 moles Cl⁻
------------------------ x ----------------------- = 12 moles Cl⁻
1 mole MgCl₂
