A 15.27 g sample of Mo2O3(s) is converted completely to another molybdenum oxide by adding oxygen. The new oxide has a mass of 18.33 g. Add subscripts below to correctly identify the empirical formula of the new oxide.
Mo2O3 has mass 15.27g
% Mo in Mo2O3 = (2*95.94/239.88)*100 = about 80% but you should do that more accurately.
Out of a 15.27g sample, 15.27 x 80% = about 12.2 g Mo and the rest is oxygen.
If you started with 12.2 g Mo there must be 12.2 g in the new oxide which means oxygen in the new oxide is 18.33-12.21 = about 6g.
mols Mo = 12.2/95.94 = about 0.13
mols O = 6/16 = about 0.38
Find the ratio of Mo to O. The easy way to do that is to divide the smaller number and the other number by itself; ie, 0.13/0.13 = 1.00 Mo and 6/0.13 = 2.9 O which rounds to Mo1O3 or MoO3.
You can go through and clean up the numbers which will make the ratio come out a little better.
m k
Well, Mo2O3(s) became a new oxide with a mass of 18.33 g? That's quite a transformation! It must have been a Mo2O5, as it gained weight like it's been binging on snacks. It's like the Mo2O3 went to the gym and came out as a heavier Mo2O5. Talk about an oxide gaining mass!
To find the empirical formula of the new oxide, we need to calculate the mole ratios of the elements present.
1. Determine the moles of Mo2O3:
moles of Mo2O3 = mass of Mo2O3 / molar mass of Mo2O3
The molar mass of Mo2O3 can be calculated by summing the atomic masses of each element:
Mo: 2 x atomic mass of Mo
O: 3 x atomic mass of O
2. Determine the moles of O in Mo2O3:
moles of O = (moles of Mo2O3) x (3 moles of O / 1 mole of Mo2O3)
3. Subtract the moles of O in Mo2O3 from the total moles of O in the new oxide:
moles of O in new oxide = moles of O - moles of O in Mo2O3
4. Determine the moles of Mo in the new oxide:
moles of Mo = (moles of Mo2O3) - (2 moles of Mo / 1 mole of Mo2O3)
5. Divide the moles of each element by the smallest number of moles obtained to get the mole ratio:
moles of Mo2O3:moles of O in new oxide:moles of Mo in new oxide
6. Convert the mole ratios to whole numbers by multiplying by a factor if necessary.
Once we have the mole ratios, we can write the empirical formula of the new oxide by using the Atomic symbols and the ratios found.
To determine the empirical formula of the new oxide, we need to calculate the mole ratio between the different elements present.
1. Determine the moles of each element:
- Mo2O3(s): Mo = 2 * Atomic mass of Mo = 2 * 95.95 g/mol = 191.9 g/mol
O = 3 * Atomic mass of O = 3 * 16.00 g/mol = 48.0 g/mol
- New Oxide: Mo = Mo (since no change in the number of Mo atoms)
O = Mass of New Oxide - Mass of Mo = 18.33 g - 15.27 g = 3.06 g
Next, we need to convert the masses of Mo and O to moles by dividing by their respective molar masses.
Moles of Mo in the new oxide = Mo mass / Atomic mass of Mo = 3.06 g / 95.95 g/mol ≈ 0.032 moles
Moles of O in the new oxide = O mass / Atomic mass of O = 3.06 g / 16.00 g/mol ≈ 0.191 moles
2. Divide the moles by the smallest value:
Divide both the moles of Mo and O by 0.032 (the smallest value) to get the simplest whole-number ratio.
Moles of Mo in the new oxide: ≈ 0.032 moles ÷ 0.032 moles = 1 mole (approx.)
Moles of O in the new oxide: ≈ 0.191 moles ÷ 0.032 moles ≈ 6 moles
Therefore, the empirical formula of the new oxide is MoO6.