The molecular mass of an organic acid was determined by the study of its barium salt. The barium salt contains two moles of water of hydration per Ba 2 + ion. 2.562 gm of this salt reacts completly wi

Question

The molecular mass of an organic acid was determined by the study of its barium salt. The barium salt contains two moles of water of hydration per Ba 2 + ion. 2.562 gm of this salt reacts completly with 30 ml of 0.2 M H 2 ​ SO 4 ​ to produce BaSO 4 ​ and the acid. The acid is monobasic. What is the molecular weight of anhydrous acid? ( Ba = 137 )

TestHub · Accepted Answer

Since the acid (HA) is monobasic, its hydrated barium salt has the formula BaA₂ ⋅ 2H₂O.

Moles of H₂SO₄ = Molarity × Volume (L) = $0.2 \times 0.030 = 0.006$ mol = moles of salt.

Molar mass of hydrated salt = $\frac{M a ss}{M o l es} = \frac{2.562}{0.006} = 427$ g/mol.

Mass of anion (A): $137 + 2 A + 2 (18) = 427 \Rightarrow 2 A = 254 \Rightarrow A = 127$ g/mol.

Molecular weight of anhydrous acid (HA) = $1 + 127 = 128$ g/mol.

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