Entries Tagged 'The Phase Rule' ↓

The diagram consists of,

i)   Curve AC The freezing point curve of A. the point A represents the freezing point of A. A is equilibrium with liquid solution B to A.Curve Be the freezing point curve of B. The point B represents the freezing point of B. B is equilibrium with liquid solution A in B applying the reduced phase rule equation to the equilibrium by the curve AC and CB

F= C-P+1

= 2-2+1

= 1

ii) The area above the curve AC and BC. Hence the two components A and B presented a liquid solutions of varying compositions

F=C-P+1

= 2-1+1

= 2

iii)The eutective point C: the two curve AC and BC meet at the point C. Here both the solids A and B must be equilibrium with the solution phase. The number of phase is

We have,

F`= C-P+1

= 2-3+1

=0

Effect of cooling:

When the A/B solution at any point in the area above ACB is cooled, the cooling dashed line meets the curve AC say at Y. here solid A separate and the equilibrium shifts down along the curve AC. The change of composition and tempareture continues till the eutectic point c is reached when solid B also separates. Thus in the area below AC and F line,.

The exist two phases viz, solid A and solution A/B.

When the solid compound and liquid phase have identical composition at the maximum point on the freezing point curve , the corresponding temperature is said to be the congruent meeting point of the compound.

The Mg and Zn system:

The phase diagram appears to be made of two simple eutective diagrams, the one toward the left present the system Mg-Mgzn2

i)                   Curve AC,CD,BE

ii)                Area

iii)              Eutective point C and E

iv)              Congruent point D

i)The curve AC shows the melting point is of Mg(65)is lowered on the addition of Zn. This continues until the po C is reached. The curve CD shows the increase of concentration Zn with the rise of temperature. At the maximum point D. The point D, represents H2 melting point of Mg2r2(575 c). the curve De now shows the lowering of the melting point with the addition of ZNC until the lowest point is attained.

The curve Be exhibits that the melting point of Zn(420c) falls with the addition of Mg. Until the point E is reached. Along the freezing point curve, AC,CD,BE there are two phases in equilibrium one solid phase and one liquid phase

We have,

F=C-P+1

=2-2+1

= 1

ii) the Area: The area above the curve AC,CD,BE represent the solution of Mg and Zn.

iii)Eutective point C and E: there are two  eutective point  C and E ,

C= solid Mg, solid Mgzn2, liquid

E= solid Zn, solid Mgzn2 , liquid

We have , F= C-p+1= 2-3+1=0

iv)Congruent melting point :  As already stated , the composition of the compound Mgzn2 and the melt at this identical. The corresponding  temperature is the congruent melting point of the compound .Here the system has two phases , the solid compound and the melt. Both these can be represented by one component (Mgzn2)

F=c-p+1= 1-2+1=0.

It is a one component 4 phases system the four phases are :

i)                   Solid Rhombic (Sr)

ii)                Solid Monoclinic (Sm)

iii)              Liquid Sulpher (Sl)

iv)              Vapour Sulpher (Sv)

The diagram for the sulphur system is given below:

the salient feature of phase diagram:

i)                   There are 6 lines

ii)                4 areas

iii)              3 critical point

iv)              Metastable Continue reading →

Under normal conditions the system water is a three- phase one component system. The phase diagram of water is given as follows:

The salient feature of the diagram are,

i)                   3 lines, OA,OB,OC

ii)                3 areas ,AOB,AOC,BOC

iii)              1 critical point o Continue reading →

The occurance of the same substance in more that one crystalline forms is known as polymorphism, rhombic and monoclinic sulphar are two polymorphs or allotropes of sulphure.

Allotropes can be divided into three types:

i)                   Enantiotropy

ii)                 Monotropy

iii)               Dynamic.