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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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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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 ...
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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 ...
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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 ...
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1answer
52 views

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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55 views

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....
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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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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 do ...
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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 ...
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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, ...
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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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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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287 views

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 ...
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Is Raoults Law valid if the solute is non volatile but have less vapour pressure than pure solvent?

We know that on adding a non-volatile solute to a pure solvent its vapour pressure increases because of the reluctance of solute to evaporate(i.e. strong intermolecular forces of attraction) Instead ...
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1answer
282 views

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 ...
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Derivation of freezing-point depression equation

Can anyone provide me the real derivation of depression in freezing point? In almost all of the books and online articles that I have read, it says $\Delta T_\mathrm{f}$ is directly proportional to ...
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2answers
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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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269 views

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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1answer
884 views

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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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 ...
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291 views

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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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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Freezing point lowering for a mixture of many liquids

I have been taught that if I have a solute of molality $m$ mixed with a liquid, the freezing point in lowered by an amount $K_\mathrm{f}\cdot m$ where $K_\mathrm{f}$ is the molal freezing depression ...
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Does the mole fraction of a solution change with Vant Hoff factor?

I reason that as mole fraction is a measure of colligative properties, increase in the Vant Hoff factor ( and hence increase in the value of colligative properties) should also leave a mark on the ...
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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?
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Is there any difference between isotonic and isosmotic solution?

Is there any difference between isotonic and isosmotic solution? Can we say isotonic solution do not show osmosis because they have same osmotic pressure?
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1answer
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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 ...
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137 views

Intuitive explanation for depression of freezing point

Why does depression of freezing point takes place if a non-volatile solute is added to the solution? For more details about the question checkout this link below Depression of freezing point
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1answer
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Why it is very rare to find a compound that lacks carbon to be liquid at standard temperatures and pressures?

It is the first time I heard such a generalization, I had no idea. Why being liquid in standard conditions is special to compounds which contain carbon atom? Which property of carbon cause this?
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145 views

Proper explanation for depression of freezing point [closed]

Why does depression of freezing point takes place if a non-volatile solute is added to the solution? Depression of freezing point
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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 ...
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641 views

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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1answer
294 views

What happens to the gas inside cold drinks as the cold drink is frozen?

According to Henry's law the amount of gas dissolved is directly proportional to the pressure exerted by a gas on the surface of the liquid. And we know if we increase the temperature, the amount of ...
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403 views

Finding molar mass of naphthalene using the freezing point of a solution?

Naphthalene is the main ingredient in some mothballs. The freezing point of a solution made by dissolving $\pu{7.01 g}$ of naphthalene in $\pu{200 g}$ of benzene is $4.20 \pu{^\circ C}$ . What is ...
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Why is osmotic pressure the best colligative property? [closed]

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 instead of molality. As compared ...
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How does dry air get saturated in the Ostwald-Walker Method?

This question was already asked and this was the answer that was posted: "So basically, before you start the experiment the vapors have already formed, meaning that thermodynamic equilibrium has been ...
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Is my proof valid for the formula of elevation in boiling point? [closed]

Is my proof valid for the formula of elevation in boiling point? proof By Clausius clayperon equation, $$\ln(P)=-\frac{∆H_v}{RT}+c$$ Differentiating, $$\frac{dP}{...
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Why does only a single azeotropic composition exist for a mixture of two given substances?

In the image below, which represents a generic composition vs. temperature plot for a mixture, there is a single intersection point between the vapor and liquid curves. This is due to the fact that ...
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How to determine the highest freezing point by van't hoff factor when concentration is same? [closed]

Whch of the following will have the highest freezing point? a) 0.1M KCl b) 0.1M glucose c) 0.1M BaCl2 d) 0.1M AlCl3
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How do repulsive solute interactions affect the van't Hoff factor?

Context. Consider an ideal solution, one in which the intermolecular solvent-solvent, solute-solute, and solute-solvent interactions are all equal. The presence of a solute therefore produces (solely) ...
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Relationship between freezing point depression and hydrogen bonds

Freezing point of a solvent is decreased due to the added solute particles in it. e.g. ions. Therefore electrolytes contribute to lowering freezing point (say for physiological conditions). If a ...
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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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928 views

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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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 ...
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Order of molecular mass of solvent; given boiling point [closed]

Given three solvents X, Y, Z. Order of boiling point of pure solvent X < Y < Z and same order of molal elevation constant ($K_\mathrm{b}$). Find the order of molecular mass. So I got this ...