A 20.0 % by mass solution of phosphoric acid (H₃PO₄) in water has a density of 1.114 g/mL at 20^$\circ$C. What is the molarity of this solution A) 0.0114 M B) 0.0568 M C) 0.114 M D) 2.27 M E) 11.4 M

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Quizplus · Accepted Answer

The molarity of the solution can be calculated by first determining the mass of phosphoric acid in 1 liter of solution. Since the solution is 20.0% by mass phosphoric acid, this means there are 200 grams of phosphoric acid in 1000 mL of solution (since the density is 1.114 g/mL, 1 liter of solution has a mass of 1114 grams). The molar mass of phosphoric acid (H3PO4) is approximately 98 g/mol, so the number of moles of phosphoric acid in 200 grams is 200 g / 98 g/mol ≈ 2.04 mol. Therefore, the molarity of the solution is 2.04 M, which is closest to choice D, 2.27 M.

A 200 % by Mass Solution of Phosphoric Acid (H3PO4) in in Water

A 200 % by Mass Solution of Phosphoric Acid (H₃PO₄) in in Water