Question Detail
Question
How many grams of MgCl₂ is needed to obtain 5.0 × 10²³ Mg²⁺ ions?
Correct Answer
Option B is the correct answer.
Detailed Explanation
Moles Mg²⁺ = (5.0 × 10²³)/(6.022 × 10²³) = 0.8305 mol. Each MgCl₂ gives 1 Mg²⁺, so moles MgCl₂ = 0.8305 mol. Molar mass MgCl₂ = 24 + 71 = 95 g/mol. Mass = 0.8305 × 95 = 78.9 g.
Hint
Use Avogadro's number to find moles, then multiply by molar mass.