The (15-35-15) number on a bag of fertilizer is calculated by an outdated method. Using the knowledge of the old methods, the number of moles of phosphorus found in 10.0 grams of phosphorus is 0.05 mole.
The (15-35-15) number on the bag of fertilizer is used for:
- Nitrogen 15 : Phosphorus pentoxide 35: potassium oxide 15
Thus, in a 100-gram bag of fertilizer, there are 35 grams of phosphorus pentoxide P₂O₅.
∴
To determine the number of moles of 10 grams of phosphorus pentoxide in (15-35-15) bag of fertilizer, we have:
= 3.5 grams of P₂O₅
Recall that:
- the molar mass of P₂O₅ = 142 g/mol
∴
Provided that 1 mole of P₂O₅ harbors 2 moles of phosphorus;
Then;
The number of phosphorus present in 10.0 grams of (15-35-15) fertilizer is:
= 0.0246 moles × 2
= 0.0492 moles
≅ 0.05 moles
Therefore, we can conclude that the number of moles of phosphorus found in 10.0 grams of (15-35-15) bag of fertilizer is 0.05 moles.
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