1. Which one of the following is the structure of hexa Meta phosphate? X represents monovalent alkali metal.
a) X5P3O10
b) (XPO3)6
c) PO4-3
d) X4P2O7∙YH2 O
Explanation: The structure of meta phosphate is PO3–, on combining X and PO3– we get XPO3. Hence hexa Meta phosphate structure is (XPO3)6.
2. What is the chemical formula for sodium Tri polyphosphate?
a) Na4P2O7
b) Na3PO4
c) NaPO3
d) Na5P3O10
Explanation: The chemical structure of poly phosphate is X5P3O10. Hence the chemical formula for sodium tri polyphosphate is Na5P3O10 which is formed by the combination of 1 mole of monosodium to 2 moles of disodium phosphate.
3. What is the molecular weight of Na5P3O10?
a) 368
b) 363
c) 360
d) 365
Explanation: The atomic weights of sodium, phosphorous, oxygen are 23, 31, and 16 respectively. Hence the total molecular weight is (23*5) + (31*3) + (16*10) = 368.
4. What ratio of Na2O/P2O5 is required to form of 1 mole of monosodium to 2 moles of disodium phosphate?
a) 1.87
b) 1.62
c) 1.67
d) 1.82
Explanation: Soda ash solution and concentrated H3PO4 are diluted in a batch mixing tank. A 1.67 ratio of Na2O/P2O5 is required to form of 1 mole of monosodium to 2 moles of disodium phosphate.
5. Which type of rotary dryer is used in manufacture of sodium tri polyphosphate?
a) Rotary drum dryer
b) Indirect fired and cooled rotary dryer
c) Rotary vacuum dryers
d) Direct rotary dryers
Explanation: The sodium tri polyphosphate solution is filtered, dried, cooled and annealed along the length of the indirect fired and cooled rotary drier.
6. Super phosphate grade of calcium phosphate is formed by reacting with which of the following acid?
a) H2SO4
b) HCl
c) H3PO4
d) HNO3
Explanation: Superphosphate grade of calcium phosphate is produced by the reaction of phosphate rock with sulfuric acid, H2SO4.
7. What is the percentage of P2O5 present in triple super phosphate?
a) 16-20%
b) 42-50%
c) 30-35%
d) 62-70%
Explanation: Super phosphate contains 16-20% P2O5 whereas triple super phosphate contains 42-50% P2O5. These are 2 distinct grades of calcium phosphate.
8. What is the chemical formula of super phosphate?
a) CaH4 (PO4)2
b) Ca3 (PO4)2
c) CaH4 (PO4)2∙CaSO4
d) (Ca3 (PO4)2)3∙CaF2
Explanation: Chemical formula of super phosphate formed by reaction of phosphate rock with sulfuric acid containing 16-20% P2O5 is CaH4 (PO4)2∙CaSO4.
9. What is the chemical formula of triple super phosphate?
a) (Ca3 (PO4)2)3∙CaF2
b) CaH4 (PO4)2
c) Ca3 (PO4)2
d) CaH4 (PO4)2∙CaSO4
Explanation: Chemical formula of triple super phosphate formed by reaction of phosphate rock with phosphoric acid containing 42-50% P2O5 is CaH4(PO4)2.
10. What is the reaction time of triple super phosphate formation?
a) 15-20 min
b) 5-6 min
c) 5-15 min
d) 20-30 min
Explanation: Acid is mixed with ground rock in a continuous mixer, which is sent into continuous belt reactor where reaction completes in 15-20 min.