Molality used in Colligative Properties

“Colligative” has been derived from the Latin word “colligates”, which mainly means “bound together”. 

These properties do not depend on the solution component’s chemical nature. Several qualities convey the concentration of a solution, like morality, polarity, and normality. Therefore these colligative properties can be linked. 

Overview of Molality

The amount of solute moles available or present in a total of 1 kg of a solvent is known as the molality of the solution. Molality is represented by the letter m. For example, a gram of solute with a molecular mass of b present in a gram of solvent.

• Molality is a calculation that considers the mass of liquids rather than their volume. As a result, it is the most practical way of describing solution concentration.
• Unlike the mole fraction approach, this method is not affected by temperature changes.
• Molality and solubility have the following relationship:

Formula of Molality

Molality= Moles of solute kilograms of solvent

The molal concentration of the solution is denoted by the letter m. The amount of moles of solute per kg of a solvent is known as molality. However, we now understand that molality is determined by:

M = (1000 × w2) ÷ (w1 × M2)

In this scenario,

The molar mass of the solute is M2, and its weight is w2.

The solvent weights w1.

Why is Molality used in Colligative properties?

Colligative properties depend on several solution particles like relative lowering of vapour pressure, elevation in boiling point and depression in freezing point. In these quantities, temperature increases when we add solute to the solvent. As we know that molality is the number of solute moles available or present in a total of 1 kg of a solvent which remains constant concerning temperature. That’s why molality can be used in colligative properties, as the weight of the solvent is not changing with temperature.

Mole

The current definition of one mole is based on the most stable form of carbon, carbon-12. However, it turns out that you can also understand the number of atoms in a mole in terms of a very different natural standard – the nuclear mass of helium. 

• This approach reveals that Avogadro’s number is 6.022141 × 1023. That’s not a minor difference. In terms of the different definitions, one mole equals not 6.022 × 1023 atoms but 6.02198 × 1023 atoms. Just as using eggs instead of atoms changed our mole concept, this discovery would change our understanding of a mole if we adopted it as the official standard for how many molecules are in a mole.

n = N/NA

NA = Avogadro Number

N = number of moles

N = number of elementary entities

• For Avogadro’s number to have any significance, the masses of all atoms and molecules in nature must be created equal. All sorts of evidence suggest that this is indeed true. Measurements of the masses of light atoms such as oxygen and hydrogen agree with the calculated mass from their constituent parts. 
• It’s hard to imagine that hydrogen could have been lighter or heavier than what we find now. But most measurements made over a century ago failed to show any variation in the weights of heavier atoms. They all tended to weigh roughly the same, no matter their atomic number. 

(moles) (molar mass) → mass

Moles (grams/mole) = grams

(mass/molar mass) → moles

(grams/grams/mole) = grams (mole/grams) = moles

Mole Concept

There is a standard way of expressing amounts of substances in chemistry for use in equations and calculations. It is the mole concept, which assigns a number to the amount of substance present. 

• This follows from the atomic mass unit and can be used in all chemical calculations. With the mole concept and molar masses, it is essential to know how they work. 
• The molecular mass and mole concept is not only helpful for carrying out chemical calculations but also provides essential information about how reactants and products are related. 
• For example, knowing that hydrochloric acid has a mass-to-volume ratio of 35 gives us a way to compare the amounts of HCl and water that react together, whether the amounts are measured in grams or millilitres.

Some Important Formulas

1. Mass of 1 mole of atoms = Atomic Mass in grams
2. Several moles of atoms = Mass of elements in grams/Relative Atomic Mass
3. Mass of 1 mole of molecules = Molecular Mass in grams
4. Number of moles of molecule = Mass of the substance in grams/Relative Molecular Mass
5. Mass of substance containing 1 mole of particles = Molar Mass
6. Percentage Yield = Atomic Mass of the product obtained/Theoretical mass of the product received.

Conclusion 

Colligative qualities can be utilised to precisely calculate a substance’s molality. The qualities employed include:

• The osmotic pressure.
• The boiling point elevation.
• The freezing point depression and the relative vapour pressure reduction.

Mole concept is an inherent part of a substance’s atomic properties and general chemistry. Atoms and molecules are the smallest of all objects in size and mass. When discussing weight, the molar mass may indicate the weight of one sample mole.