Find the mass of phosphorus that is formed by the interaction of 120 g of calcium phosphate
Find the mass of phosphorus that is formed by the interaction of 120 g of calcium phosphate containing 20% impurities with sand and coke if the mass fraction of the phosphorus yield is 85%?
Let’s find the mass of calcium phosphate without impurities.
100% – 20% = 80%.
120 g – 100%,
X – 80%,
X = (120 g × 80%): 100% = 96 g.
Let’s find the amount of phosphorite substance by the formula:
n = m: M.
M (Ca3 (PO4) 2) = 40 × 3 + 2 (31 + 16 × 4) = 310 g / mol.
n = 193.75 g: 310 g / mol = 0.31 mol.
Let’s compose the reaction equation, find the quantitative ratios of substances.
Ca3 (PO4) 2 + 5 C + 3SiO2 = 3CaSiO3 + 2P + 5CO.
According to the reaction equation, there is 2 mol of phosphorus per 1 mol of Ca3 (PO4) 2. The substances are in quantitative ratios of 1: 2.
The amount of phosphorus will be 2 times more than the amount of Ca3 (PO4) 2.
n (P) = 2 n (Ca3 (PO4) 2) = 0.31 × 2 = 0.62 mol.
Let’s find the mass of phosphorus by the formula:
m = n × M,
M (P) = 31 g / mol.
m = 0.6 mol × 31 g / mol = 19.22 g.
19.22 g was obtained according to calculations. According to the condition of the problem, the yield is 85%.
19.22 – 100%,
X – 85%.
X = (19.22 × 85%): 100% = 16.34 g
Answer: 16.34 g.