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Molality Calculator
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Molality is defined as "the number of moles of solute dissolved in 1kg (1000g) of solvent." Molality often finds application in physical chemistry, where it is often necessary to consider the quantities of solute and solvent separately, rather than as a mixture.
Molality Calculator determines the amount of solute dissolved in a given quantity of solvent or solution.
 

Steps for Molality Calculator

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Step 1 :  

Read the problem carefully and identify the values given for the moles of the solute and weight of the solvent.



Step 2 :  

Apply the molality formula and substitute the given values in order to get the molality value.


Molality(M): $\frac{Number\ of\ moles\ of\ solute}{Weight\ of\ solvent\ in\ kg}$



Step 3 :  

Check the molality values are in specified units.



Problems on Molality Calculator

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  1. If 250c.c solution contains 4g NaOH , find out the molality of the solution, if the density of the solution is 1.02g/ml.


    Step 1 :  

    From the data
    Weight of solution = 250c.c $\times$ 1.02g/c.c = 255g
    Hence weight of solvent = (255-4) = 251g



    Step 2 :  

    Molality = $\frac{4}{40}$ $\times$ $\frac{1000}{251}$ = 0.392.



    Step 3 :  

    The molality is expressed as 0.392 mol/kg.



    Answer  :  

    The molality of the given solution is 0.392 mol/kg.



  2. Concentrated HCl is 37% by weight, calculate the molality of the solution.


    Step 1 :  

    From the data 100g solution contains 37g HCl.
    Hence weight of solvent = (100-37) = 63g



    Step 2 :  

    Molality = $\frac{W}{M}$ $\times$ $\frac{1000}{weight\ of\ solvent}$

    = $\frac{37}{36.5}$ $\times$ $\frac{1000}{63}$

    = $\frac{37000}{2299.5}$ = 16.09



    Step 3 :  

    The molality is expressed as 16.09 mol/kg



    Answer  :  

    The molality of the given concentrated HCl solution is 16.09 mol/kg.



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