Question

How much mess of solut of NaOH are desolved in 500g of water to produce 3 molal solution
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Answer 1

Answer:

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The molecular weight of NaOH is 40 g/mol.

The number of moles of NaOH

40 g/mol

5 g

=0.125 moles.

500 ml water corresponds to0.500 L.

The molarity of the solution =

0.500 L

0.125 moles

=0.25 M

Answer 2

Answer:

Molality is the number of moles of a substance per 1 kg of solvent. Therefore 1.5 kg water contains the number of moles (3 ) expressed in gms of the NaOH, multiplied by 1.5/1.

ie ( 3 x 40) x 1.5/1 gm of NaOH, or 180 g.

This is not to be confused with molarity which is the number of moles of substance in a final solution volume of 1 litre. Thus, the molarity has a slightly higher concentration than the molality. However, as the solute concentration approaches zero with a water temperature at 4 C, the molality and molarity converge to the same value.Molality is the number of moles of a substance per 1 kg of solvent. Therefore 1.5 kg water contains the number of moles (3 ) expressed in gms of the NaOH, multiplied by 1.5/1.