Question

The label of a fertilizer states that the fertilizer contains 18.0% P₄O₁₀ by mass. What is the mass percentage of phosphorous in the fertilizer?

Answer 1

100g of fertilizers contains 18.0g of P4O10. Thus, moles of P4O10 can be calculated as follows:

Moles of P4O10 = Wt. of P4O10 / molar mass of P4O10

Moles of P4O10 = (18.0 g) / (283.89g/mol)

Moles of P4O10 = 0.0634

One mole of P4O10 contains four moles of phosphorous (P). Thus, number of moles of P can be calculated as follows:

Number of moles of P = 4 x moles of P4O10

Number of moles of P = 4 X 0.0634

Number of moles of P = 0.2536

Thus, mass of P can be calculated as follows:

Mass of P = moles of P x molar mass of P

Mass of P = 0.2536 mol x (31.0 g/mol)

Mass of P = 7.9 g

Since, mass of P in 100g of fertilizer is 7.9g. Therefore, mass percentage of phosphorous in the fertilizer is 7.9%