## Question

The density of 3 M solution of NaCl is 1.25 g mL^{–1}. Calculate the molalityof the solution.

### Solution

2.79 m

3 M NaCl solution meants that 3 moles of NaCl are present in 1 L of the solution.

Mass of 1 L, *i.e.,* 1000mL of the solution

=

=

Mass of 3 moles of solute (NaCl)

= 1074.5 g = 1.0745 kg

= 2.79 mol kg^{–1} = 2.79 m

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