Calculate the amount of phosphorus (V) oxide substance, which is formed by burning 350 g of red phosphorus containing 10% impurities.
m (P) = 450 g
w% (impurities) = 10%
m (P2O5) -?
4P + 5O2 = 2P2O5, – we solve the problem based on the composed reaction equation:
1) Find the mass of pure phosphorus without impurities:
if the proportion of impurities in the composition of the substance is 10%, then the proportion of pure phosphorus is 90%.
m (P) = 450 g * 0.9 = 405 g
2) Find the amount of phosphorus:
n (P) = m: M = 405 g: 31 g / mol = 13.06 mol
3) We compose a logical expression:
if 4 mol of P gives 2 mol of P2O5,
then 13.06 mol of P will give x mol of P2O5,
then x = 6.53 mol.
Answer: n (P2O5) = 6.53 mol.
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