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 10.10 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 10.07 mL of 0.08444 M potassium permanganate (KMnO4) to reach the purple endpoint. A blank required 0.08 mL. Determine the percent WO3 in the ceramic sample.

To determine the percent WO3 in the ceramic sample, we will use a redox titration method. We will start by understanding the chemical reactions involved in the titration.

The equation for the reduction of tungsten trioxide (WO3) to tungsten trioxide (W3) using Pb(Hg) is as follows:

WO3 + 3Pb(Hg) -> W3 + 3Pb + 3Hg

Next, the W3 is transferred to a solution of hydrochloric acid (HCl), resulting in the formation of tungstic acid:

W3 + 6HCl -> H2WO4 + 3H2 + 3Cl2

Then, potassium permanganate (KMnO4) is used as the titrant, which oxidizes tungstic acid to permanganate while being reduced to manganese(II) ions:

H2WO4 + 2KMnO4 + 8HCl -> H2WO4 + K2WO4 + 2MnCl2 + 8H2O

Now, let's calculate the amount of WO3 in the ceramic sample.

1. Calculate the number of moles of KMnO4 used in the titration:
Volume of KMnO4 used = 10.07 mL
Concentration of KMnO4 = 0.08444 M

Moles of KMnO4 used = (Volume x Concentration) / 1000
= (10.07 mL x 0.08444 M) / 1000
= 0.0008496 mol

2. Calculate the moles of WO3 in the aliquot:

From the balanced equation, we know that 1 mole of KMnO4 reacts with 2 moles of H2WO4.

Therefore, Moles of H2WO4 = (0.0008496 mol KMnO4) / 2
= 4.248 x 10^-4 mol H2WO4

Since we started with a 100.00 mL aliquot, we assume that the entire aliquot contains the same amount of H2WO4.

Therefore, Moles of H2WO4 in the entire solution = (4.248 x 10^-4 mol H2WO4) / (100.00 mL / 1000)
= 4.248 x 10^-3 mol H2WO4

3. Calculate the moles of WO3 in the entire solution:

From the balanced equation, we know that 1 mole of H2WO4 reacts with 1 mole of WO3.

Therefore, Moles of WO3 = 4.248 x 10^-3 mol H2WO4

4. Calculate the mass of WO3 in the ceramic sample:

Mass of WO3 = (Moles of WO3 x Molar mass of WO3) / Mass of the sample
= (4.248 x 10^-3 mol x 231.84 g/mol) / 10.10 g
= 0.097 g

5. Finally, calculate the percent WO3 in the ceramic sample:

Percent WO3 = (Mass of WO3 / Mass of the sample) x 100
= (0.097 g / 10.10 g) x 100
= 0.96%

Therefore, the ceramic sample contains approximately 0.96% WO3.