Tungsten trioxide (WO3) has a rich yellow color and is often used as a pigment i

Question

Tungsten trioxide (WO3) has a rich yellow color and is often used as a pigment in ceramics and paints. In order to test a ceramic vase for its WO3 content, a 10.14 g sample of the vase was ground and reduced with Pb(Hg) to convert any WO3 to W3 . The resulting W3 was transferred to 500.0 mL of 1.00 M HCl. A 100.00 mL aliquot of the HCl solution required 11.03 mL of 0.08084 M potassium permanganate (KMnO4) to reach the purple endpoint. A blank required 0.09 mL. Balance the reaction below and determine the percent WO3 in the ceramic sample.

Question 12 of 13 Map Sapling Learning Tungsten trioxide (WO3) has a rich yellow color and is often used as a pigment in ceramics and paints. In order to test a ceramic vase for its WO3 content, a 10.14 g sample of the vase was ground and reduced with Pb(Hg) to convert any WO3 to W3+. The resulting W3+ was transferred to 500.0 mL of 1.00 M HCI. A 100.00 mL aliquot of the HCI solution required 11.03 mL of 0.08084 M potassium permanganate (KMnO4) to reach the purple endpoint. A blank required 0.09 mL. Balance the reaction below and determine the percent WO3 in the ceramic sample. Number %WO, Previous Give Up & View Solution e check Answer Next Exit Hint

Explanation / Answer

balanced reaction :

3MnO4^- + 5W^3+ + 4H^+(aq) ---> 3Mn^2+ + 5WO2^2+ + 2H2O(l)

no of mol of KMnO4 reacted = 11.03*0.08084/1000 = 0.000892 mol

   from equation, 3 mol MnO4^- = 5 mol W^3+

no of mol of w^3+ present in sample = 0.000892*5/3 = 0.0015 mol

no of mol of w^3+ = no of mol of WO3

no of mol of wo3 = 0.0015 mol

mass of wo3 present in sample = 0.0015*232 = 0.348 g

% WO3 in sample = 0.348/10.14*100 = 3.42%

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