With this molality calculator friend can quickly calculate the molality - one way of measuring the concentration that a solute in a solution (not come be puzzled with molarity). Simply type the number of moles of your solute substance and also mass that the solvent and the tool will calculate the molality. If you don't understand how many moles that a substrate friend have, usage the advanced mode to calculation it through the usage of mass and molar mass of the compound. Room you still unsure what's the molality definition, its units and also formula - or simply exactly how to calculate molality action by step? save reading and also you'll find the answer!

Molality meaning and molality formula

Molality, additionally called molal concentration, is characterized as the lot of problem of solute, divided by the mass of the solvent m solvent:

Molality = nsolute / m solvent = msolute / (W solute * m solvent)


nsolute is amount of the solute (in moles)msolvent is a massive of the solvent (in kg)msolute is a massive of the solute (in g)W solute is a molar massive of the solute (in g/mol).

You are watching: What is the mole fraction x of solute and molality

The molality unit from SI device is mol/kg, occasionally the name molal is offered (though it's considered obsolete).

Molarity vs molality

Molarity and also molality are similar concepts - both are actions of concentration the a solution. However, over there is one key difference between those terms: molarity is expressed as the amount of substance per unit volume of solution, conversely, molality specifies the concentration together the amount of substance per unit massive of the solvent.

We've placed all most necessary differences in between those 2 terms into a short molarity vs molality table:

Molarity Molality
Definition Amount of substance (in moles) split by the volume (in litres) of the solution Amount of substance (in moles) divided by the mass (in kg) the the solvent
Symbol M m or b
Unit mol/L mol/kg
Temperature and also pressure dependent independent
Usage an ext popular, helpful to use in the lab, faster and also easier accurate but rarely used

To adjust between molarity and molality you deserve to use the adhering to relation:

M = m * d / (1 + (m * W))


M - molaritym - molalityW - molar fixed of the soluted - mass thickness of the solution

How to calculate molality with this molality calculator

Let's display on the instance how to calculation molality:

Choose your substance. Let's assume it's table salt - salt chloride (NaCl).Calculate that molar mass. For sodium chloride it's equal to 58.44 g/mol (as Na = 22.99 g/mol and Cl = 35.45 g/mol).Convert grams to moles. Use the formula mole = fixed of solute / molar mass. Assume we desire to dissolve 70.128 grams of salt in 1.5 kg that water. So mole NaCl = 70.128 g / (58.44 g/mol) = 1.2 mol.

See more: Did Leah Williams, Qvc, Have Weight Loss Surgery? Leah Has Lost Weight

Plug moles value and also the fixed of the solvent right into the molality formula. Division 1.2 mol by 1.5 kg, and also you'll find out the the molality that the NaCl systems is 0.8 molal (in conventional molality units: 0.8 mol/kg).Or save yourself some time and also use ours molality calculator (choose an breakthrough mode come enter also the molar mass and solute mass).