How to Find out the Value of a Colligative Property of a Solution – Part 1

Colligative properties are those properties of solutions which depend on the ratio of the number of solute particles to that of solvent particles in a solution, and not on the nature of the chemical species present.


The van 't Hoff factor is a measure of the effect of a solute on colligative properties, viz., relative lowering in vapor pressure, boiling-point elevation, freezing-point depression and osmotic pressure, and is the ratio of the actual (experimental/observed) concentration of particles produced when the substance is dissolved to the formal (theoretical/normal) concentration that would be expected from its chemical formula. For most non-electrolytes dissolved in water, the factor is basically 1.

Osmotic pressure is the minimum pressure which needs to be applied to a solution to prevent the inward flow of its pure solvent across a semipermeable membrane.

Chemical equilibrium is the state in which both the reactants and products in a chemical reaction are present in concentrations that have no more propensity to change with time, s.t. there is no visible alteration in the system properties.

This state results when the forward reaction proceeds at the same rate as the reverse/backward reaction, and is known as dynamic equilibrium.

Mnemonic: ICE: Initial Change Equilibrium (concentration or partial pressure)

Question:

An M/10 solution of K4[Fe(CN)6] is 50% dissociated at 300 K. Calculate the osmotic pressure of the solution.

Solution:



Click to enlarge the image

α = Degree of dissociation, π = Osmotic pressure, i = van ‘t Hoff factor, C = Concentration, R = Gas constant, T = Absolute temperature

Crazy colligative properties❓ Let Chemaficionado know at mychemistryhomework@gmail.com❗

References:

(1)    Wikipedia Contributors. Chemical equilibrium. Wikipedia. https://en.wikipedia.org/wiki/Chemical_equilibrium.

‌(2)    Wikipedia Contributors. Raoult’s law. Wikipedia. https://en.wikipedia.org/wiki/Raoult%27s_law.

(3)    Colligative properties. Wikipedia. https://en.wikipedia.org/wiki/Colligative_properties.

(4)    Wikipedia Contributors. van 't Hoff factor. Wikipedia. https://en.wikipedia.org/wiki/Van_%27t_Hoff_factor.

‌(5)    Wikipedia Contributors. Osmotic pressure. Wikipedia. https://en.wikipedia.org/wiki/Osmotic_pressure.

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