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61.

The electric furnace is used for the manufacture of elemental phosphorus from a phosphate rock. The fused section of the furnace where the reduction to elemental phosphorus takes place is maintained at

A.	500-600?C	B.	800-900?C
C.	1400-1450?C	D.	2000-2100?C

62.

Yellow phosphorus is converted to red phosphorus in covered retorts at a temperature of

A.	250-450?C in absence of air	B.	100-150?C in absence of air
C.	1400-1450?C in absence of air	D.	800-1000?C in absence of air

63.

Yellow phosphorus is transported under

A.	air	B.	nitrogen
C.	water	D.	all of these answers

64.

The electric furnace is used for the manufacture of elemental phosphorus from phosphate rock. The electrodes are made of

A.	carbon	B.	aluminium
C.	zinc	D.	copper

65.

The chemical formula of othophosphoric acid is

A.	H3PO3	B.	H3PO4
C.	H4P2O7	D.	HPO3

66.

The chemical formula of pyrophosphoric acid is

A.	H4P2O7	B.	H3PO4
C.	HPO3	D.	H3PO3

67.

The chemical formula of metaphosphoric acid is

A.	H4P2O7	B.	HPO3
C.	H3PO3	D.	H3PO4

68.

Which one of the following oxy-acids of phosphorus is derived from oxide different from the one from which the other three acids are derived?

A.	H3PO4	B.	H4P2O7
C.	HPO3	D.	H3PO3

69.

Raw materials for the manufacture of orthophosphoric acid by wet process are phosphate rock and

A.	coke	B.	98% H2SO4
C.	sand	D.	60% HNO3

70.

In wet process (strong sulphuric acid leaching) for the manufacture of orthophosphoric acid the reactor temperature is maintained at

A.	80?C	B.	200?C
C.	250?C	D.	900?C