Questions tagged [colligative-properties]

Colligative properties of solutions are properties that depend upon the concentration of solute molecules or ions, but not upon the chemical identity of the solute.

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How is lowering in vapour pressure a colligative property?

Imagine we have two containers: A and B. Both contain equal amounts of water and we add (say 50) molecules of sucrose and 50 molecules of glucose in containers A and B respectively. Now, the typical ...
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3 answers
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How salt helps to melt ice even when there is no dynamic equilibrium between water and ice?

I am a high school student and I am confused about freezing point depression. We say that when in winter's it gets even colder than normal freezing point Temperature then we use solute to melt ice ...
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Freezing of a beverage

I am trying to generally describe the process of freezing beer and how the different ingredients influence the freezing process. My general approach right now is to observe a beer as 90% water and 10% ...
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An experiment to study colligative properties

I was planning on doing a school project on the effects of gelatin on the melting point of water, as follows: Aim: To study the variation in the melting point of water mixed with gelatin. Materials ...
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Determining the molar mass of a substance by the osmotic pressure as a function of a mass concentration

Let's say that I have a solution of some substance in some solvent. The density of the solute is $\rho_\text{solute}$ and the density of the solvent is $\rho_\text{solvent}$. Suppose that the osmotic ...
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2 answers
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Explanation for Raoults Law

The vapour pressure of pure liquids is independent of quantity of substance. But when in a solution, the vapour pressure of the components are given by $$P_A=P^°_AX_A$$$$P_B=P^°_BX_B$$ Since $A-A$, $A-...
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Why does the osmotic pressure method offer an advantage over other methods of molar mass calculation? [closed]

Measurement of osmotic pressure provides another method of determining molar masses of solutes. This method is widely used to determine molar masses of proteins, polymers and other macromolecules. The ...
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2 answers
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Why is molality measured in terms of the solvent instead of the whole solution? [duplicate]

The molality $b$ of a solute dissolved in a solvent is given by: $$b_\mathrm{solute} = \dfrac{n_\mathrm{solute}}{m_\mathrm{solvent}}$$ where $n_\mathrm{solute}$ is the amount of solute (e.g. in mol) ...
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What is the derivation for the expression of depression in freezing point?

In my textbook, it is written that the expression for depression in freezing point is $$\Delta T_\mathrm f=K_\mathrm f\cdot m$$ where $\Delta T_\mathrm f$ is the freezing point depression (defined as ...
2 votes
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Eutectic plot - freezing point lowering

I have a doubt about the correlation between eutectic plots and freezing point lowering. The freezing point lowering, as well as all colligative properties, is defined in the presence of a volatile ...
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Colligative properties and binary phase diagrams

I'm having troubles with colligative properties and how to relate them to binary liquid-vapour and solid-liquid phase diagrams. First of all, in my book it is indicated that colligative properties are ...
8 votes
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Detailed kinetic explanation for vapor pressure reduction by dissolved solute?

The following problem was asked in JEE Mains 2020 (Sept 2, Shift 1), An open beaker of water in equilibrium with water vapor is in a sealed container. When a few grams of glucose are added to the ...
1 vote
1 answer
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How to calculate the freezing point of an equimolar ethanol: water mixture using colligative properties [closed]

I am familiar with how to calculate the freezing point of a mixture with a 9:1 molar ratio of ethanol to water (see below). I can understand that ethanol, having a higher mole fraction, is considered ...
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1 answer
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Is vapour pressure truly a colligative property?

Colligative properties are generally defined as A colligative property depends only on the ratio of the number of particles of solute and solvent in the solution, not the identity of the solute. ...
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Why does freezing point decrease when vapour pressure decreases in dilute solutions?

I was studying colligative properties of dilute solutions, and one of the properties was freezing point depression. The confusion I had was that, if vapour pressure decreases, it should be easier to ...
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2 answers
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Is vapour pressure a surface phenomenon?

As a fact, I know that vapour pressure doesn't depend on surface area. Does this imply it is not a surface phenomenon also? It shouldn't be as then it would depend on surface area of molecules and ...
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Best method for molecular mass determination

A number of different methods may be employed for determination of molecular mass of any sample. But I want to limit our focus to the following methods, Relative lowering of partial pressure ...
5 votes
1 answer
762 views

The relationship of the osmotic pressure of a polymeric solution and its the molecular mass

Why is the osmotic pressure of a polymeric solution decreases when the molecular mass is increasing? I am honestly unsure if the above statement is true, at least it seems to me to be true. When I ...
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1 answer
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Osmolality and osmolarity of infant formula

Actually, this question is about the following sentence, which I have seen (in various forms) in numerous papers (e.g. this one and this one): The American Academy of Pediatrics advises that formulas ...
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Does Raoult's law hold for immiscible liquids?

I know that Raoult's law holds true only for a non volatile solute in a volatile solvent mixture wherein the vapour pressure of the solution gets lowered due to the addition of solute. Now, first of ...
3 votes
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Do lyophilic sols have an electrical double layer?

"There are two factors which are responsible for the stability of lyophilic sols. These factors are the charge and solvation of the colloidal particles". Quoted from NCERT book of OC But we ...
1 vote
1 answer
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Understanding the Osmotic Pressure formula

$$\Pi = iMRT$$ Can this be rewritten as $\Pi = ORT$ where $O =$ osmolarity? The only reason I ask is because my book doesn’t talk about the relationship between osmolarity and molarity, but I came ...
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Finding freezing temperature and osmotic pressure of an ethylene glycol and glycerol solution in water

A water solution is prepared by mixing $\pu{200 g}$ of a ethylene glycol (ethan-1,2-diol; $\ce{C2H6O2}$) solution (20% by weight) with $\pu{500 g}$ of glycerol (propan-1,2,3-triol; $\ce{C3H8O3}$) ...
40 votes
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Which "exotic salt" can lower water's freezing point by 70 °C?

The Medium.com article Mars Phoenix Lander, 10 Years Later shows several remarkable images and discoveries on Mars by the Mars Phoenix Lander circa 2008. One image (shown below) shows what looks like ...
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1 answer
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Camphor for molecular mass determination

I came across this statement in my book that read, "Camphor is used to determine the molecular mass of substances because it has a high value of cryoscopic constant." What does this have to ...
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Relative lowering of vapour pressure

Why is lowering of vapour pressure (Po - Ps) temperature dependent? And why is relative lowering of vapour pressure (1 - Ps/Po) independant of temperature?
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Why is the boiling point of sugarcane juice lower than the boiling point of water?

As the boiling point is a colligative property, one would expect that the boiling point of sugarcane juice should be higher than pure water because Sugarcane juice contains water (75–85%), non-...
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Colligative properties: why does the size of solute not matter?

Colligative properties are defined as the "properties of solutions that depend on the ratio of the number of solute particles to the number of solvent molecules in a solution, and not on the ...
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Why is water transferred from a beaker of pure water to a beaker of sugar solution when placed in the a closed container?

I know that there is something to do with the vapour pressure of pure water being higher than the vapour pressure of the sugar solution, but I still can’t really explain what happens on a molecular ...
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2 answers
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Why do we use molality on describing colligative property?

I'm satisfied with the explanation about Raoult's law that the chance of vaporizing will depend on the surface exposed to the atmosphere and solute will decrease such chance by taking portion of the ...
2 votes
1 answer
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How to calculate the depression in freezing point of a solution in which there are multiple solutes being added?

In just about every problem I've encountered earlier, all such questions describe the process for calculating the depression in freezing point for a solution wherein there is only one solute. However, ...
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1 answer
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What happens to depression when two solutions are mixed? [closed]

Equal volumes of $\pu{1.0 M}$ $\ce{KCl (aq)}$ and $\pu{1.0 M}$ $\ce{AgNO3 (aq)}$ solutions are mixed. The depression of freezing point of the resulting solution (with respect to water) will be (assume ...
1 vote
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How to determine the van't Hoff factor for different salts in water experimentally?

How do I experimentally determine the van't Hoff factor for different salts in water? I'm going to dissolve each of sodium chloride, potassium chloride, and lithium chloride in $\pu{20 mL}$ of water ...
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Finding the reduced pressure to distill a solution containing 0.4 g of naphthalene in 25 g of chloroform at 50 °C

Chloroform boils at $\pu{62 ^\circ C}$. For a solution containing $\pu{0.4 g}$ of naphthalene in $\pu{25 g}$ of chloroform, the boiling point is elevated by $\pu{0.45 K}$, to avoid any decomposition ...
1 vote
1 answer
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Boiling point elevation with multiple solutes

I've encountered a problem where glucose and $\ce{NaCl}$ are mixed with water and $\Delta T$ is to be calculated. I've calculated $\Delta T$ for both glucose ($i = 1$) and $\ce{NaCl}$ ($i = 2$) ...
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1 answer
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Molality of solution to be used when finding water separated from solution as ice

Question $\pu{1 kg}$ of a solution of cane sugar is cooled and maintained at $\pu{-4 ^\circ C}$. How much ice will separate out if molality of solution is $0.75$? $K_\mathrm{f} \ \text{(water)} = 1....
1 vote
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Are colligative properties applicable for volatile liquids and gases in liquid solvent? Why/Why not?

My teacher told me that the expressions for calculation of colligative properties like lowering in freezing point are only applicable if the solute is non volatile liquid or a solid. We cannot apply ...
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Does the boiling point of an aqueous solution depend on what the solute is?

Consider a situation where we have two aqueous solutions which have the same concentration (e.g. 1 M), but the solute is different. For example, one is a solution of glucose, and the other is a ...
6 votes
1 answer
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How to approximate the pH of a box of water molecules with one proton?

I have a cubic box of length $L = 12.42\ \mathrm{\overset{\circ}A}$, containing $60\ \ce{H2O}$ molecules and $1\ \ce{H+}$ ion. How can I approximate the $\mathrm{pH}$ of the system? Following the ...
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1 answer
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Deviations from Raoult's Law [closed]

A solution of two compounds may be an ideal solution and follow Raoult's Law, or it may show a positive or negative deviation from Raoult's Law. How to predict that whether a solution of two given ...
8 votes
1 answer
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The connection of the "R" in the ideal gas law and osmotic pressure [closed]

I am studying chemistry and biology at the same time, and have encountered a problem. In the ideal gas law, the $R$ is the ideal gas constant, and its value is $\pu{0.0821 L atm mol-1 K-1}.$ However, ...
1 vote
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How to find relative lowering of vapour pressure from phase diagrams in terms of temperature?

Problem Answer My question Does a tie rule exist for solution solvent phase diagram to express relative lowering of vapour pressure in terms of temperature? The phase diagram is the one ...
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3 answers
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Colligative properties of colloids [closed]

The following lines are from my textbook: Colloidal particles being bigger aggregates, the number of particles in a colloidal solution is smaller than a true solution. Hence, the values of ...
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1 answer
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Why is measurement in molarity preferred over molality?

NCERT Chemistry Part 1 states that: "The osmotic pressure method has the advantage over other methods as pressure measurement is around the room temperature and the molarity of the solution is used ...
1 vote
1 answer
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Elevation in boiling point of water [closed]

$\pu{1060 g}$ of urea aqueous solution is subjected to heating. It starts boiling at $\pu{100.53 °C}.$ It is heated up to $\pu{102.12 °C}.$ Find amount of water vapourised in grams. (Pure water ...
1 vote
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Do colligative properties depend on the number of solute molecules?

Colligative properties are properties that are affected by the number of solute molecules dissolved in the solution. True or false? I think the statement is false, and the correct one should use "...
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Freezing Point Depression and Temperature Decrease

I don't have a problem understanding the chemical mechanisms underlying freezing point depression or colligative properties in general, but what I cannot seem to grasp is how if you add salt to ice ...
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How much salt (or any other substance one can find in a kitchen) do I need to add to make water boil at 104 °C?

I've seen some formulas around in other questions and Google searches, but my chemistry is pretty much dead so I have no clue where to find the relevant values to calculate it myself. I just need to ...
4 votes
3 answers
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Why do colligative properties depend only on number of solute particles?

Colligative properties depend solely on the number of even though the interactive forces are different for different solute-solvent pairs. So why is the dependence only on the number of solute?
2 votes
1 answer
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Depression of freezing point [closed]

Recently, I learnt that by adding a non-volatile solute to a solvent, the vapour pressure of the solution is decreased and consequently its boiling point. Facts and definitions freezing point: "The ...