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 10.21 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 11.36 mL of 0.08569 M potassium permanganate (KMnO4) to reach the purple endpoint. A blank required 0.18 mL. Balance the reaction below and determine the percent WO3 in the ceramic sample.

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 10.21 g sample of the vase was ground and reduced with Pb(Hg) to convert any wo3 to he resulting was transferred to 500.0 mL of 1.00 M HCI. A 100.00 mL aliquot of the HCI solution required 11.36 mL of 0.08569 M potassium permanganate (KMno4) to reach the purple endpoint. A blank required 0.18 mL. Balance the reaction below and determine the percent wo3 in the ceramic sample. Mnoi 3+ 2+ Mn WO Number WO

Explanation / Answer

W3+ --> W6+ +3 e-
MnO4- + 5 e- + 8 H+ --> Mn2+ + 4 H2O
Balancing for electrons yields:
5 W3+ --> 5 W6+ + 15 e-
3 MnO4- + 15 e- + 24 H+ --> 3 Mn2+ + 12 H2O
5W3+ + 3MnO4-+ 24H+ --> 5W6+ + 3Mn2+ + 12H2O

Moles of MnO4- at the eq point = 0.08569 *(11.3.6-0.18)/ 1000 = 0.000958 moles

these reacted with 0.000958 * 5/3 moles of M3+ at the eq point = 0.001596 moles

Moles in 500 mL = 0.001596 * 5 = 0.007983 moles of W3+

Molar mass of WO3 is 231.8382 g/mol

Mass of WO3 in the flask and sample = 0.007983 moles * 231.8382 g/mol = 1.85084163 g

% WO3 in the sample = 1.85084163 / 10.21 *100 = 18.12 %

(check the calculations if required)

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.