# if the density of a 3 M aq solution of NaCl is 1.25 g/ml, what will be its molality?

3M solution means 1000mL solution contains 3 moles of NaCl.

Hence, $1000mL\times 1.25g/mL$ $=1250g$ solution contains 3 moles of NaCl.

Mass of solvent $=1250-\left(3\times 58.5\right)=1074.5g$

1074.5 g solvent contains 3 moles NaCl

â€‹Hence 1000g solvent will contain $\frac{3}{1074.5}\times 1000=2.79$moles

Hence molarity is 2.79 m

Hope this helps,

Regards

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