MOLALITY IS DEFINED AS THE NUMBER OF MOLES OF SOLUTE DISSLOVED IN 1000 GRAMS OF SOLVENT

An alternative unit of concentration to molarity is molality. The molality of a solute is the number of moles of that solute divided by the weight of the solvent in kilograms.

number of moles of solute per kg solvent

Concentration measured by the number of moles of solute per kilogram of solvent

molality is number moles of solute dissolved per kg of solvent...............Moreover, it is considered a better concentration unit over molarity(i.e. no of moles dissolved in 1 litre of solution) because it doesn't vary with temperature.............

molality is the no. of molesof the solute present in 1000g or i kg of the solvent.

mathematically as

molality = moles of solute /mass of solvent in kg

Molality is the number of moles of solute per Kilogram of solvent.

It is denoted by 'm'.

m=no of moles/kilogram of solvent

m=wb*1000/mb*wa.

where

m--molality

wb--weight of solute

wa--weight of solvent

mb--molecular mass of solute.

*molality is independent of temperature.

molar concentration (also called molarity, amount concentration or substance concentration) is a measure of the concentration of a solute in a solution, or of any molecular, ionic, or atomic species in a given volume.

Molality (mol/kg, molal, or m) denotes the number of moles of solute per kilogram of solvent (not solution). For instance: adding 1.0 mole of solute to 2.0 kilograms of solvent constitutes a solution with a molality of 0.50 mol/kg. Such a solution may be described as "0.50 molal". The term molal solution is used as a shorthand for a "one molal solution", i.e. a solution which contains one mole of the solute per 1000 grams of the solvent.

Following the SI system of units, the National Institute of Standards and Technology, the United States authority on measurement, considers the unit symbol m to be obsolete, and suggests instead the term 'molality of substance B' (m_B) with units mol/kg or a related unit of the SI. This recommendation has not been universally implemented in academia yet.

Note: molality is sometimes represented by the symbol (m), while molarity by the symbol (M). The two symbols are not meant to be confused, and should not be used as symbols for units. The SI unit for molality is mol/kg. (The unit m means meter.)

Like other mass-based measures, the determination of molality only requires a good scale, because masses of both solvent and solute can be obtained by weighing, and molality is independent of physical conditions like temperature and pressure, providing advantages over molarity.

In a dilute aqueous solution near room temperature and standard atmospheric pressure, molarity and molality will be very similar in value. This is because 1 kg of water roughly corresponds to a volume of 1 L at these conditions, and because the solution is dilute, the addition of the solute makes a negligible impact on the volume of the solution.

However, in all other conditions, this is usually not the case.

no. of moles of solute present in per kg. of solvent is called molality.