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If a solution contains 4.00 moles of MgCl2 in 40.0 moles of water, what is the mass percent concentration of MgCl2? Answer to three significant figures. |
Answer» Given:-→ Number of moles of MgCl₂ = 4.00 → Number of moles of WATER = 40.0 To find:-→ Mass percent concentration of MgCl₂. Solution:-[Mg = 24 g/mol ; Cl = 35.5 g/mol] Molar mass of MgCl₂ :- = 24 + 35.5×2 = 24 + 71 = 95 g/mol [H = 1 g/mol ; O = 16 g/mol] Molar mass of water (H₂O) :- = 1×2 + 16 = 18 g/mol ________________________________ Mass of MgCl₂ in the solution :- = No of moles × Molar mass = 4 × 95 = 380g Mass of water in the solution :- = No of moles × Molar mass = 40 × 18 = 720g ________________________________ Mass percent concentration of MgCl₂ :- = 380/[380 + 720] × 100 = 380/1100 × 100 = 38000/1100 = 34.5% THUS, required concentration is 34.5% . |
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