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A solution is prepared that is 23.44 wt% NaCl in water. What is the molality of the...

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user9937478 | eNotes Newbie

Posted January 30, 2013 at 3:49 AM via web

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A solution is prepared that is 23.44 wt% NaCl in water. What is the molality of the solution? 

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jeew-m | College Teacher | (Level 1) Educator Emeritus

Posted January 30, 2013 at 4:21 AM (Answer #1)

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Molality is the ratio between amount of substance of solute in moles and amount of solvent in kg.

Molality (M) = (moles of solute)/(mass of solvent)

 

Here the solute is NaCl and solvent is water.


23.44% wt means we have 23.44g of NaCl in 100ml of water.


For 1000ml of water we have `23.44xx10 = 234.4` g of NaCl.

 

Molic weight of NaCl = 58.44g/mol

 

moles of NaCl `= 234.4/58.44 = 4.01` moles

 

So we have 4.01 moles of NaCl in 1000ml of water.

Usually 1ml of water has a weight of 1g.

So in the solution we have 1000g = 1kg of water.

 

Molality = 4.01/1 = 4.01mol/kg

 

The molality of the NaCl solution is 4.01mol/kg

 

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