 이 브라우저는 더 이상 지원되지 않습니다. 업데이트하여 최적의 YouTube 환경과 최신 기능을 이용하세요. 자세히 알아보기 Show Answer Hint: The freezing point and the molality of the solution is related with each other by the colligative property known as depression in freezing point. The molality is the number of moles of solute dissolved in one kilogram of solvent. Complete step by step answer: The relation between the molality and the freezing point is known by the depression in freezing point.The depression in freezing point is one of the colligative properties. The colligative property is defined as the property of the solution which is dependent on the concentration of the solute particles and not on the nature of the solute particles.The freezing point depression is defined as the lowering of the freezing point of the solvent by the addition of the solutes which can be explained using Raoult’s law. According to Raoul's law when a nonvolatile solute is added in the solvent, the vapour pressure of the solvent decreases by the addition of solute.The freezing point is defined as the point at which any substance present in the liquid state starts to freeze.The depression in freezing point is given by the formula as shown below.$\Delta {T_f} = i \times {K_f} \times m$Where,$\Delta {T_f}$ is the depression in freezing point.i is the Van’t Hoff factor${K_f}$ is the cryoscopic constantm is the molalityThe depression in freezing point is directly proportional to the molality of the solution where the molality is the number of solute dissolved in one kilogram of the solvent.When, the $T_f^0$ is the freezing point of the pure solvent, ${T_f}$ is the freezing point of the solution and $\Delta {T_f}$ is the depression in freezing point.So, the freezing point of the solution will be given as$\Delta {T_f} = T_f^0 - {T_f}$So, when more concentrated will be the solution in other words more number of solute particles, the freezing point will be depressed more.Note: The formula of the depression in freezing point is also used to determine the molecular weight of the compound by using the formula of molality. To calculate the molecular weight the mass should be known. Answer Verified Hint: By using the formula of depression in freezing point one can determine the relation between the freezing point and the molecular weight. The depression in freezing point is equal to the product of cryoscopic constant and molality. Complete step by step answer: The freezing point depression is explained as the lowering of the freezing point of the solvent with the addition of the solute.The freezing point depression is the colligative property which is proportional to the molality of the solute added.The freezing point depression is given by the formula as shown below.$\Delta {T_f} = {K_f} \times m$Where,$\Delta {T_f}$ is the freezing point depression${K_f}$ is the cryoscopic constantm is the molalityThe molality is defined as the number of moles of solutes dissolved in one kilogram of solvent.The formula of molality is shown below.$m = \dfrac{n}{{{M_1}}}$Where,m is the molalityn is the number of moles${M_1}$ is the mass in kilogramThe number of moles is given by the formula as shown below.$n = \dfrac{m}{{{M_2}}}$Where,n is the number of molesm is the mass${M_2}$ is the molecular weightSo, if we substitute the terms in the formula of freezing point depression then the new formula obtained will be.$ \Rightarrow \Delta {T_f} = {K_f} \times \dfrac{m}{{{M_2}{M_1}}}$If we keep the ${K_f}$, m and ${M_1}$ as constant then the freezing point depression will be inversely proportional to the molecular weight.$ \Rightarrow \Delta {T_f} = \dfrac{1}{{{M_2}}}$So, by increasing the value of depression in freezing point, the molecular weight decreases and vice versa.Thus, an increase in the molecular weight will have a smaller effect on the freezing point. Note: The freezing point is calculated by subtracting the depression in freezing point value and the freezing point of pure water which is zero degree Celsius.Freezing point depression refers to the lowering of the freezing point of solvents upon the addition of solutes. It is a colligative property of solutions that is generally proportional to the molality of the added solute. The depression in the freezing point of a solution can be described by the following formula. ΔTf = i×Kf×m Where
Freezing Point Depression in Solutions As per Raoult’s law, “the vapour pressure of a pure solvent decreases with the addition of a solute”. Since the vapour pressure of a non-volatile solvent is zero, the overall vapour pressure of the solution is lesser than that of the pure solvent. Recommended VideosWhy does the Freezing Point Depression Occur?The reason for the depression of the freezing point of a solvent upon the addition of a solute is explained below.
A graph detailing the freezing point depression of water upon the addition of sucrose to it is provided below. Freezing Point Depression Graph From the graph, it can be observed that the increase in the molality of sucrose causes further depression in the freezing point of the solvent (water). Freezing Point Examples
The normal freezing point and the corresponding freezing point depression is tabulated below.
Uses of Freezing Point DepressionSome important uses of freezing point depression are listed below.
Freezing point, when a liquid becomes a solid. Increased pressure, as with the melting point, typically increases the freezing point. Bringing a seed crystal into a supercooled liquid causes freezing, resulting in the release of fusion heat increasing the temperature to the freezing point rapidly.
Liquids have a temperature characteristic at which they become solids, known as their freezing point. Theoretically, a solid’s melting point should be the same as the liquid’s freezing point. During the action, it is possible to observe small differences between these quantities.
Fusion, vaporization and sublimation are endothermic processes, while exothermic processes are freezing, condensation, and deposition.
Water freezes when it hits 32 degrees Fahrenheit (0 degrees Celsius), but the amount of time it takes to do so depends on several variables that may vary from your neighbour’s in your freezer.
The six-phase changes are freezing, boiling, condensing, vaporizing, sublimating, and deposition. To learn more about this property of solutions and other colligative properties, such as the elevation in boiling point, register with BYJU’S and download the mobile application on your smartphone.
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What is freezing point depression give the relation between depression in freezing point of a solution and the molecular weight of the solute dissolved in it?
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