Define Molal Elevation Constant And Molal Depression Constant QnA (2024)

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What do you mean by molal elevation constant and molal depression constant? ›

The units of molal elevation constant represented by is. = change in boiling point. = Molal elevation constant. m = molality. Molal depression constant is defined as the depression in freezing point when the molality of the solution is unity, i.e 1 mole of the solute is dissolved in 1 kg of the solvent.

Molal depression and elevation constants for water Kf and Kb are 1.86∘C kg mol−1 and 0.512∘C kg mol−1 respectively.

Kf is a constant for a given solvent. Kf is called the molal freezing point depression constant and represents how many degrees the freezing point of the solvent will change when 1.00 mole of a nonvolatile nonionizing (nondissociating) solute dissolves in one kilogram of solvent.

Molal depression constant for a solvent is 4.0 k g m o l − 1 . The depression in the freezing point of the solvent for 0.03 m o l k g − 1 solution of K 2 S O 4 is: (Assume complete dissociation of the electrolyte). A solvent X freezes at 240∘C.

Molal depression constant depends only on the nature of the solvent.

Depression of freezing point (ΔT_f) for dilute solution (ideal solution) is directly proportional to molality, m of the solution. The proportionality constant, K_f, depends on the nature of the solvent. It is also known as Freezing Point Depression Constant or Molal Depression Constant, or Cryoscopic Constant.

The molal elevation constant depends upon the characteristics of the solvent, because the changes associated in boiling point with a solution of unit concentration will get significantly impacted by the strength of interactions present inside the solvent molecules.

Boiling point elevation is the difference in temperature between the boiling point of the pure solvent and that of the solution. The molal boiling-point elevation constant is equal to the change in the boiling point for a 1-molal solution of a nonvolatile molecular solute.

The molal elevation constant for water is 0.56 K kg mol−1.

How to calculate freezing point depression? The equation for freezing point depression is T=i*Kf*m, where T is the change in freezing point, i is the van't Hoff factor, Kf is the freezing point depression constant, and m is the molality of the solution.

What is the value of molal depression constant for water? ›

Molal depression constant for water is 1.86°C.

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Molal depression constant can be defined as the depression in freezing point produced when one mole of non-volatile solute is dissolved in 1 kg i.e. 1000 g of the solvent. It is also known as the cryoscopic constant.

Answer: molal elevation constant is related to boiling point while as molar elevation constant is related to melting point.

Colligative property is the property which depends on the relative amount of solute present in the pure solvent. If the relative amount of solute increases in the solvent the boiling pont also increases,so boiling point is colligative property.

The relationship between these two constants depends on the molecular weight of the solute. Thus, in general, we cannot say that the molecular elevation constant is equal to 10 times the molal elevation constant.

The ebullioscopic constant is also called the molal elevation constant. It is defined as the elevation in boiling point when one mole of non-volatile solute is added to one kilogram of solvent. It is denoted by K_b. The unit of an ebullioscopic constant is K Kg mol^-1.

The molal elevation constant is the elevation in the boiling point of a solvent when one mole of a non-volatile solute is dissolved in it per kilogram of solvent. The unit of molal elevation constant is given as Kkgmol−1. Here, m is molality or the number of moles of the solute dissolved in a kg of solvent.