What is depression in freezing point?

Freezing point of a substance is the temperature at which solid and liquid phases of the substance coexist. It is defined as the temperature at which its solid and liquid phases have the same vapour pressure.

The freezing point of a pure liquid is preset. Now, if a non-volatile solute is dissolved in the pure liquid to constitute a solution, there occurs a lowering in the freezing point. The freezing point of solution refers to the temperature at which the vapour pressure of the solvent in two phases, i.e. liquid solution and solid solvent is the same. Since the vapour pressure of the solvent at a lower temperature.

Evidently the freezing point of the pure solvent is the temperature corresponding to the point B (T0 K) and that of the solution is the temperature corresponding to the point A'(T1 K). Clearly, (T0 - T1) or ΔTƒ is the freezing point depression. Since its magnitude is determined by that of lowering of vapour pressure, the freezing point depression depends upon the molal concentration of the solute and does not depend upon the nature of solid. It is, thus, a colligative property. The general relation between these two quantities for a solution of non-electrolyte is usually expressed in term of molality of the solution

ΔTƒ  Δp and Δp xB

ΔTƒ = kxB =

For dilute solution,    and hence,.

ΔTƒ = k   = kMA

If WA is the mass of solvent in kg, then   is equal to molality (m) of the solution

ΔTƒ = kMAm     (? kMA = Kƒ)

ΔTƒ =Kƒm, where Kƒ is called Freezing point depression constant or molal depression constant or cryoscopic constant.

As is clear from the above, depression in freezing point depends upon relative number of moles of solute and solvent but does not depend upon nature of solute, so it is a colligative property.

#### Related Questions in Chemistry

• ##### Q :Biodegradable polymers what are the

what are the examples of biodegradable polymers

• ##### Q :Thermodynamics 1 Lab Report I already

I already did Materials and Methods section. I uploaded it with the instructions. Also, make sure to see Concept Questions and Thinking Ahead in the instructions that I uploaded. deadline is tomorow at 8 am here is the link to download all instructions because I couldn't attach all of t

• ##### Q :Some basic concepts of chemistry an

an atom of an element is 10.1 times heavier than the mass of a carbon atom.What is its mass in amu?

• ##### Q :Mole fraction of water and ethanol Give

Give me answer of this question. A solution contains 1 mole of water and 4 mole of ethanol. The mole fraction of water and ethanol will be: (a) 0.2 water + 0.8 ethanol (b) 0.4 water + 0.6 ethanol (c) 0.6 water + 0.8 ethanol (d) 0.8 water + 0.2 ethanol

• ##### Q :Moles of chloride ion Select the right

Select the right answer of the question. A solution of CaCl2 is 0.5 mol litre , then the moles of chloride ion in 500ml will be : (a) 0.25 (b) 0.50 (c) 0.75 (d)1.00

• ##### Q :Molar mass Select the right answer of

Select the right answer of the question. Which is heaviest: (a)25 gm of mercury (b)2 moles of water (c)2 moles of carbon dioxide (d)4 gm atoms of oxygen

• ##### Q :Organic and inorganic substances living

living beings are made up of organic and inorganic substances.according to their complexity of their molecules how can ach of these substances be classified?

• ##### Q :Dissolving Group IV Carbonate Explain

Explain how dissolving the Group IV carbonate precipitate with 6M CH3COOH, followed by the addition of extra acetic acid.

• ##### Q :Problem on Molar solution Can someone

Can someone please help me in getting through this problem. 2.0 molar solution is acquired, when 0.5 mole solute is dissolved in: (i) 250 ml solvent (ii) 250 g solvent (iii) 250 ml solution (iv) 1000 ml solvent

• ##### Q :Coordination compounds discuss the

discuss the practical uses of coordination compounds, give reactions involves and explain whats happening in the process