Assertion :Elementary phosphorus exists in three principal allotropic forms, i.e., white (or yellow), red (or violet) and black. Reason: Of the three forms, white phosphorus is the most important and most reactive.

Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

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Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

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Assertion is correct but Reason is incorrect

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Both Assertion and Reason are incorrect

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Solution

The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

Elemental phosphorus exists in several allotropic forms, the most common are white and red. White (or yellow) phosphorus is very reactive and will immediately inflame in the air so it is stored under water.
The other common form of phosphorus is red phosphorus which is much less reactive and is one of the components on the striking surface of a matchbox.

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Similar questions

Q. ASSERTION:

Δ_{f} H^{o}

for white phosphorus has been taken to be zero, whereas black phosphorus is the most stable allotrope of phosphorus and this is the only exception.

REASON:
The reference standard state of white phosphorus is taken despite the fact that this form is not the most stable allotrope but simply the most reproducible form of phosphorus.

Q. Assertion: The impurities such as

{SiO}_{2}

present in iron ore is removed by

{CaCO}_{3}

.

Reason:

CaO

formed by decomposition of

{CaCO}_{3}

reacts with

{SiO}_{2}

to form slag.

Assertion – The non-fusible impurities present in iron ore are removed by $C a C O_{3}$ .

Reason: $C a C O_{3}$ which decomposes into $C a O$ and $C O_{2}$ . The $C a O$ formed reacts with $S i O_{2}$ to remove silica

Assertion (A) Order and molecularity are same.

Reason (R) Order is determined experimentally and molecularity is the sum of the stoichimetric coeffcient of rate determining elementary step.

(a) Both assertion and reason are correct and the reason is correct explanation of assertion
(b) Both assertion and reason are correct, but reason does not explain assertion.
(c) Assertion is correct, but reason is incorrect
(d) Both assertion and reason are incorrect
(e) Assertion is incorrect but reason is correct.

Q. Assertion: The compressibility factor for

H_{2}

and

H e

(1 + \frac{P b}{R T})

Reason: The compressibility factor for

H_{2}

and

H e

can be derived from Van der Waal's equation.

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