Determine the mass of phosphorus (V) oxide during the combustion of 20 g of phosphorus.

univerkov | February 28, 2021 | education

4P + 5O2 = 2P2O5
According to the periodic table, we determine the molar masses of phosphorus and its oxide: M (P) = 31 g / mol; M (P2O5) = 31 * 2 + 16 * 5 = 142 g / mol.
Let’s find the amount of phosphorus substance: n = m / M = 20 g / 31 g / mol = 0.645 mol.
According to the reaction from 4 mol of phosphorus, we get 2 mol of oxide, then n (P2O5) = 0.645 * 2/4 = 0.3225 mol.
Find the mass of the oxide: m = n * M = 0.3225 mol * 142 g / mol = 45.8 g.
Answer: the mass of phosphorus oxide is 45.8 g.

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