PLease help me out with a couple of doubts that I have in regard to eutectic mixtures...
1. Why is the
composition of a eutectic mixture at the eutectic pint fixed?
How could it be otherwise?
Or do you mean why is it not a range?
But you look at the melting temperatures as a function of say tin% you get a curve with the lowest point at eutectic.
spark
21st September 2009 - 06:24 PM
By that particular question,I meant that....
Before the eutectic point,lead started freezing at a certain temperature (lower than the normal freezing point of lead) and proceeded to freeze gradually.All this time,the tin is molten,but all of a sudden,at (62% of lead-38% of tin composition),both freeze.
How does the mixture know that since its at the eutectic composition,it has got to completely freeze?
Now,another two small questions...
1.When we are cooling the mixture,how can small amounts of lead separate out at a time,since we are lowering the temperature of the entire mixture --the entire lead should freeze all at once,shouldn't it?
2.In the phase diagram of the eutectic mixture,we have two temperature axes..If we draw a line vertically downward parallel to the temperature axis,what would the points all the way along the vertical line denote?
Enthalpy
25th September 2009 - 11:14 PM
It's 62% (or rather 63%) tin, not lead.