The oxidation of phosphine (PH3) to phosphorus pentoxide (P2O5) is given by the chemical equation:

Question

2PH3 + 4O2 → P2O5 + 3H2O

How many grams of O2 will react completely with 35.0 grams of PH3?

Answer 1

To find out how many grams of O2 will react completely with 35.0 grams of PH3, we need to first determine the molar mass of PH3 and O2.

Molar mass of PH3:
1 atom of phosphorus (P) = 30.97 g/mol
3 atoms of hydrogen (H) = 3.03 g/mol

Molar mass of PH3 = 30.97 + 3.03 = 34.00 g/mol

Molar mass of O2:
2 atoms of oxygen (O) = 2 x 16.00 = 32.00 g/mol

Next, we need to determine the number of moles of PH3 in 35.0 grams:
Number of moles = Mass / Molar mass
Number of moles of PH3 = 35.0 g / 34.00 g/mol = 1.03 moles

From the balanced chemical equation, we can see that 2 moles of PH3 react with 4 moles of O2. Therefore, the mole ratio is 2:4 or 1:2.

Since we have 1.03 moles of PH3, we will need 2.06 moles of O2 to react completely.

Finally, we can calculate the grams of O2 needed using the molar mass of O2:
Mass of O2 = Number of moles x Molar mass
Mass of O2 = 2.06 moles x 32.00 g/mol = 65.92 grams

Therefore, 65.92 grams of O2 will react completely with 35.0 grams of PH3.