Elemental phosphorus burns in oxygen with an intensely hot flame, producing a brilliant light and clouds of the oxide product. These properties of the combustion of phosphorus have led to its being used in bombs and incendiary devices for warfare. P4(s) + 5 O2(g) → 2 P2O5(s) If 4.29 g of phosphorus is burned, what mass of oxygen does it combine with?

grams of oxygen combined with 4.29 grams of phosphorus = 5.54 grams

Explanation:

Firstly, we write the chemical equation between phosphorus and oxygen and balance it.

phosphorus is usually poly atomic and oxygen is diatomic.

P4(s) +  O2(g) → P2O5(s)

The balanced equation

P4(s) + 5O2(g) → 2P2O5(s)

Atomic mass of phosphorus = 30.973762 g/mol

Phosphorus is polyatomic = 4 × 30.973762 = 123.90 grams

Atomic mass of Oxygen = 16 g/mol

For diatomic oxygen = 2 × 16 = 32 grams

In the reaction 5 moles of oxygen = 5 × 32 = 160 grams

From the reaction

123.90 grams of phosphorus combines with 160 grams of oxygen

4.29 grams phosphorus will combine with ? grams of oxygen

cross multiply

grams of oxygen = 4.29 × 160/123.90

grams of oxygen = 686.400/123.90

grams of oxygen = 5.54 grams

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