For the allotropic forms of iron, the points of arrest are

Which of the following represents the allotropic forms of iron?

A

Alpha iron, beta iron and gamma iron

B

Alpha iron and beta iron

C

Body centered cubic iron and face centered cubic iron

D

Alpha iron, gamma from and delta iron

Points of arrest for iron correspond to

A

Stages at which allotropic forms change

B

Stages at which further heating does not increase temperature for some time

C

Stages at which properties do not change with increase in temperature

D

There is nothing like points of arrest

Two circular dials of exactly the same size are mounted on a wall side by side in such a way that their perimeters touch at one point. Dial 1, which is on the left , spins clockwise around its center , and dial 2 , which is on the right spins counter clockwise around its center . (Assume that there is no friction at the point of contact between the dials.) Each dial is marked on its perimeter at three points that are at equale distances around the points arked ondial 1 are N, O, and P and the points marked on dial 2 are X, Y, and Z. If points O and Z are just meeting at the point of contact between the dials , and if dial 1 spins at the same speed as dial 2, what is the smallest number of revolutions of each dial that will bring O and Z together again?

A

1

B

2

C

3

D

4

. Diamond is an allotropic form of

A

germanium

B

carbon

C

silicon

D

sulphur

A material is said to be allotropic, if it has

A

Fixed structure at all temperatures

B

Atoms distributed in random pattern

C

Different crystal structures at different temperatures

D

Any one of the above

A material is known as allotropic or polymorphic if it

A

Has a fixed structure under all conditions

B

Exists in several crystal forms at different temperatures

C

Responds to heat treatment

D

Has its atoms distributed in a random pattern

Heat evolved/absorbed during conversion of a substance from one allotropic form to another is termed as the heat of

A

Fusion

B

Vaporisation

C

Transition

D

None of these

Absorption/evolution of heat during conversion of a substance from one allotropic form to another is termed as the heat of

A

Sublimation

B

Fusion

C

Transition

D

Vaporisation

The most stable allotropic form of phosphorous is the __________ phosphorous.

A

White

B

Black

C

Yellow

D

Red

The most reactive allotropic form of phosphorus is __________ phosphorus.

A

Red

B

Yellow

C

Violet

D

Black

For the allotropic forms of iron, the points of arrest are

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