Question

Calculate the percentage of phosphorus in the fertilizer superphosphate Ca(H2PO4)2. (correct to 1 dp)
[H = 1 ; O = 16 ; P = 31 ; Ca = 40]

August 4, 2024

Answer

Molecular weight of Ca(H₂PO₄)₂

= 40 + 2[2(1) + 31 + 4(16)]

= 40 + 2[2 + 31 + 64]

= 40 + 2[97]

= 40 + 194

= 234 g

234 g of Ca(H₂PO₄)₂ contains 62 g of P

∴ 100 g of Ca(H₂PO₄)₂ will contain = $62\over234$ × 100

= 26.49% = 26.5%

Hence, 26.5% phosphorous is present in superphosphate Ca(H₂PO₄)₂

💡 Some Related Questions

Copper [II] sulphate soln. reacts with sodium hydroxide soln. to form copper hydroxide according to the equation :
2NaOH + CuSO4 ⟶ Na2SO4 + Cu(OH)2↓
What mass of copper hydroxide is precipitated by using 200 g of sodium hydroxide.
[H = 1, O = 16, Na = 23, S = 32, Cu = 64]

Aluminium carbide reacts with water according to the following equation :
Al4C3 + 12H2O ⟶ 4Al(OH)3 + 3CH4
(i) State what mass of aluminium hydroxide is formed from 12 g. of aluminium carbide.
(ii) State the volume of methane at s.t.p. obtained from 12 g of aluminium carbide.
[relative molecular weight of Al4Cl3] = 144 ; Al(OH)3 = 78

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[Ca = 40, N = 14, O = 16]

From the equation :
(NH₄)₂Cr₂O₇ ⟶ N₂(g) + 4H₂O(g) + Cr₂O₃
Calculate:
(i) the quantity in moles of (NH₄)₂Cr₂O₇ if 63 gm of
(NH₄)₂Cr₂O₇ is heated.
(ii) the quantity in moles of N₂ formed.
(iii) the volume in litres or dm3 of N₂ evolved at s.t.p.
(iv) the mass in grams of Cr₂O₃ formed at the same time.
[H = 1, Cr = 52, N = 14]

KClO3 ${\overset{ MnO2 }{\longrightarrow}}$ 2KCl + 3O2
(i) Calculate the mass of KClO3 required to produce 6.72 lit of O2 at s.t.p.
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(ii) Calculate the number of moles of O2 in the above volume and also the number of molecules.

P + 5HNO3 [conc.] ⟶ H3PO4 + H2O + 5NO2.
If 9.3 g of phosphorous was used in the reaction, calculate :
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(iii) The volume of NO2 produced at s.t.p.
[H = 1, N = 14, P = 31, O = 16]

Calculate the volume of oxygen required for the complete combustion of 8.8 g of propane [C3H8].
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Commercial NaOH weighing 30 g. has some NaCl in it. The mixture on dissolving in water and treatment with excess AgNO3 soln. formed a precipitate weighing 14.3 g. What is the percentage of NaCl in the commercial sample of NaOH.
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[Relative molecular mass of NaCl = 58 ; AgCl = 143]

From the equation : C + 2H2SO4 ⟶ CO2 + 2H2O + 2SO2
Calculate :
(i) The mass of carbon oxidized by 49 g of sulphuric acid [C = 12 ; relative molecular mass of H2SO4 = 98].
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A sample of ammonium nitrate when heated yields 8.96 litres of steam (measured at step.)
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(i) What volume of di nitrogen oxide is produced at the same time as 8.96 litres of steam.
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