库叶镜常数和冷冻常数之间的差异

Thekey difference沸点升高常数之间的一个d cryoscopic constant is thatebulliososcic常数与boiling point elevationof a substance whereas cryoscopic constant is related to thefreezing point depressionof a substance.

Ebullioscopic constant and cryoscopic constant are terms used mainly in thermodynamics to describe the properties of a substance in relation to the changes in temperature. These two constants give the same value for a particular substance at similar conditions via different routes.

CONTENTS

1.Overview and Key Difference
2.What is Ebullioscopic Constant
3.什么是冷冻镜的常数
4.Side by Side Comparison – Ebullioscopic Constant vs Cryoscopic Constant in Tabular Form
5.概括

What is Ebullioscopic Constant?

An ebullioscopic constant is a thermodynamic term that relates the molality of a substance to its boiling point elevation. We can denote ebullioscopic constant as Kb, boiling point elevation as ΔT and molality as “b”. The constant is given as the ratio between boiling point elevation and molality (boiling point elevation divided by molality equals ebullioscopic constant, Kb). We can give the mathematical expression for this constant as follows:

ΔT = iK_bb

In this equation, “i” is the Van’t Hoff factor. It gives the number of particles the solute can split into or forms when the substance is dissolved in a solvent. “b” is the molality of the solution formed after this dissolution. In addition to this simple equation, we can use another mathematical expression to calculate the ebullioscopic constant theoretically:

K_b= RT²_bM/ ΔH_vap

In this equation, R refers to theideal (or universal) gas constant, Tb refers to the boiling point of the solvent, M refers to the molar mass of the solvent, and ΔH_vaprefers to the molar enthalpy of vaporization. However, in the calculation of the molar mass of a substance, we can use a known value for this constant using a procedure called ebullioscopy. Ebullioscopy refers to the “boiling measurement” in Latin meaning.

沸点升高的特性被认为是界限特性，在该特性中，该特性取决于溶解在溶剂中的颗粒数，而不是这些颗粒的性质。库霉镜常数的一些已知值包括具有3.08的乙酸，苯具有2.53，樟脑为5.95，二硫化碳具有2.34。

什么是冷冻镜的常数?

A cryoscopic constant is a thermodynamic term that relates the molality of a substance to the freezing point depression. Freezing point depression is also a colligative property of substances. The cryoscopic constant can be given as below:

ΔT_f= ik_fb

Here, “i” is the Van’t Hoff factor, which is the number of particles the solute can split into or can form when dissolved in a solvent. Cryoscopy is the process we can use to determine the cryoscopic constant of a substance. We can use a known constant to calculate an unknown molar mass. The term cryoscopy comes from the Greek meaning, “freezing measurement”.

Since the freezing point depression is a colligative property, it depends only on the number of solute particles that are dissolved and not on the nature of those particles. Therefore, we can say that cryoscopy is related to ebullioscopy. The mathematical expression for this constant is as follows:

K_b= RT²_fM/ ΔH_fus

其中r是理想气体常数，m是溶剂的摩尔质量，t_f是纯溶剂和ΔH的冰点_fusis the molar enthalpy of fusion of the solvent.

What is the Difference Between Ebullioscopic Constant and Cryoscopic Constant?

Ebullioscic常数和冷冻常数是热力学中使用的术语。猫镜体常数和冷冻镜体常数之间的关键区别在于，库乳镜体常数与物质的沸点升高有关，而冷冻镜恒定与物质的冰点抑郁有关。

Below infographic summarizes the differences between ebullioscopic constant and cryoscopic constant.

概括– Ebullioscopic Constant vs Cryoscopic Constant

猫镜体常数和冷冻镜体常数之间的关键区别在于，库乳镜体常数与物质的沸点升高有关，而冷冻镜恒定与物质的冰点抑郁有关。

Reference:

1.“冷冻镜常数。”维基百科，维基梅迪亚基金会，2020年2月4日，Available here.

Image Courtesy:

1. “Freezing point depression and boiling point elevation” – Modified Freezing_point_depression_and_boiling_point_elevation.png byTomas er(CC BY-SA 3.0)通过Commons Wikimedia