Question

calculate the theoretical yield of tungsten metal from the amount of starting material

Answer 1

The reaction is

WO3+3H2 ---> 3H2O+W

So here one mole of Tungsten (VI) oxide reacts with three moles of H2 to give one mole of tungsten.

Lets say we have started with 4.00 g of tungsten (VI) oxide yield 2.80 g of tungsten metal.

The molecular weight of WO3 = 231.84 g/mol

Moles of WO3 = Mass / Molecular weight = 4g / 231.84 = 0.0172 moles

So theoretically it will give 0.0172 moles of Tungsten metal

Mass of tungsten obtained= moles X atomic weight of tungsten = 0.0172 X 183.84 = 3.16 grams

So theoretical yield = mass of WO3 X atomic weight of tungsten / molecular weight of WO3.

you can use any value of mass of WO3.