Solutions Revision Notes

Ruhul Amin Alig

A quick revision tool for the grip on the chapter.

Concentration of a solution

Concentration of a solution
The amount of solute dissolved in an unit amount of solvent.

Percentage by Mass
The fraction of a solute in a solution multiplied by 100
Percentage by mass = (mass of solute/ mass of solution) x 100

Molarity
Numbers of moles of solute in 1 liter of a solution.
Molarity = (number of moles of solute/ volume of solution in litre)

Molality
Number of moles of solute dissolved in 1 kg of a solvent.
Molality = (moles of solute/ mass of solvent in kg)

Normality
No. of f eq. of solute/Volume of solution in litres or

d m^{3}

Mole fraction of a component in the solution
No. of moles of that component/Total no. of moles of all the components

Solubility of a gas in liquid

The solubility of any gas in a particular liquid is the volume of the gas in cc that can dissolve in a unit volume of the liquid to form the saturated solution at the temperature of the experiment and under the pressure of one atmosphere.

Factors affecting the solubility of the gas in liquid

Nature of the gas and the solvent
Effect of temperature(Decreases with increase in temperature)
Effect of pressure

Henry's law

Henry's law is one of the gas laws formulated by William Henry in 1803 and states: "At a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid." An equivalent way of stating the law is that the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid:

C = k P_{g a s}

where C is is the solubility of a gas at a fixed temperature in a particular solvent (in units of M or ml gas/l)
k is Henry's law constant (often in units of M/atm)

P_{g a s}

is the partial pressure of the gas (often in units of atm)

Vapour pressure of liquid or solution

The pressure exerted by vapours over the liquid surface at equilibrium is called the vapour pressure of the liquid.
There are certain factors on which vapour pressure depends:

Surface area
Intermolecular forces
Temperature

Raoult's law

It states that the partial vapour pressure of each component of an ideal mixture of liquids is equal to the vapour pressure of the pure component multiplied by its mole fraction in the mixture.
In a solution, the vapour pressure of a component of a given temperature is equal to the mole fraction of that component in the solution multiplied by the vapour pressure of that component in the pure state.
Two miscible liquids A and B have partial pressure

p_{A}^{o}, p_{B}^{o}

and the mole fraction be

x_{A}, x_{B}

then

p_{A} = x_{A} p_{A}^{o}

p_{B} = x_{B} p_{B}^{o}

P = p_{A} + p_{B}

x_{A} p_{A}^{o} + x_{B} p_{B}^{o}

x_{A} + x_{B} = 1

Modified expression of colligative properties

Modified Expressions for Substances undergoing Association or Dissociation

Relative lowering of vapour pressure: $\frac{p ^{o} - p}{p ^{o}} = i x_{2}$
Elevation in boiling point: $Δ T_{b} = i K_{b} m$
Depression in freezing point: $Δ T_{f} = i K_{f} m$
Osmotic pressure: $π = i \frac{n}{V} R T$

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Solutions Revision Notes

Concentration of a solution

Solubility of a gas in liquid

Henry's law

Vapour pressure of liquid or solution

Raoult's law

Modified expression of colligative properties

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Solutions Revision Notes

Concentration of a solution

Solubility of a gas in liquid

Henry's law

Vapour pressure of liquid or solution

Raoult's law

Modified expression of colligative properties

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