1. Which impurity makes phosphine spontaneously ignite in air?
A.
Phosphorus trihalide
B.
Diphosphane (P2H4)
C.
Phosphorus pentoxide
D.
Hydrogen chloride
Correct Answer:
Diphosphane (P2H4)
Explanation:
Impure phosphine containing diphosphane (P2H4) spontaneously ignites when exposed to air.
2. What happens when impure phosphine is exposed to air?
A.
It freezes immediately
B.
It dissolves without reaction
C.
It spontaneously catches fire
D.
It changes into ammonia
Correct Answer:
It spontaneously catches fire
Explanation:
The presence of diphosphane in impure phosphine causes it to ignite spontaneously in air.
3. Pure phosphine differs from impure phosphine because pure phosphine generally does not do what at room temperature?
A.
Burn in oxygen
B.
Spontaneously ignite in air
C.
Contain phosphorus
D.
Exist as a gas
Correct Answer:
Spontaneously ignite in air
Explanation:
Pure phosphine is not spontaneously inflammable under ordinary conditions, whereas impure phosphine containing P2H4 ignites in air.
4. The spontaneous ignition of impure phosphine occurs mainly because of the presence of which compound?
A.
P2H4
B.
PH4Cl
C.
PCl3
D.
H3PO4
Correct Answer:
P2H4
Explanation:
Diphosphane, represented by P2H4, is the impurity responsible for the spontaneous ignition of phosphine in air.
5. In which atmosphere does impure phosphine spontaneously ignite?
A.
Nitrogen
B.
Carbon dioxide
C.
Air
D.
Hydrogen
Correct Answer:
Air
Explanation:
Impure phosphine containing P2H4 catches fire spontaneously when it comes into contact with air.
6. What visible effect may be observed when impure phosphine burns in air?
A.
Blue crystals
B.
Smoke rings
C.
Green precipitate
D.
Colourless droplets
Correct Answer:
Smoke rings
Explanation:
Burning phosphine can produce smoke rings due to the formation of phosphorus oxides in air.
7. Which statement about impure phosphine is correct?
A.
It is nonflammable in air
B.
It spontaneously ignites in air
C.
It ignites only under water
D.
It cannot react with oxygen
Correct Answer:
It spontaneously ignites in air
Explanation:
Impure phosphine contains diphosphane, which causes spontaneous ignition when the gas is exposed to air.
8. What is the role of diphosphane in impure phosphine?
A.
It prevents combustion
B.
It causes spontaneous ignition
C.
It removes oxygen from air
D.
It converts phosphine into ammonia
Correct Answer:
It causes spontaneous ignition
Explanation:
Diphosphane is the reactive impurity that makes phosphine spontaneously inflammable in air.
9. Spontaneously igniting impure phosphine is best described as phosphine mixed with which type of substance?
A.
A combustible phosphorus hydride
B.
An inert noble gas
C.
A nonreactive metal
D.
A strong alkali
Correct Answer:
A combustible phosphorus hydride
Explanation:
Diphosphane (P2H4), a phosphorus hydride impurity, is combustible and causes the phosphine mixture to ignite spontaneously in air.
10. Why does impure phosphine catch fire on contact with air?
A.
Because it contains diphosphane
B.
Because it contains nitrogen
C.
Because phosphine is always a liquid
D.
Because air contains hydrogen
Correct Answer:
Because it contains diphosphane
Explanation:
The diphosphane impurity present in impure phosphine is responsible for its spontaneous ignition in air.
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