The density of 3 M solution of NaCl is `1.25 "g mL"^(-1)`. Calculate molality of the solution.

Explanation

`"Molality"=("Moles of the solute")/("Mass of the solvent in kg")`
3 M NaCl solution means that 3 moles of NaCl are present in 1 L of the solution.
Mass of 1 L, i.e., 1000 mL of the the solution = `"Volume "xx"Density"=1000 mLxx1.245gmL^(-1)=1250g`
Mass of 3 moles of solute (NaCl)= `3molxx58.5gmol^(-1)=175.5g`
`therefore" Mass of solvent"=1250-175.5g=1074.5g=1.0745kg`
`therefore" Morality of the solution"=("3 mol")/(1.0745kg)=2.79"mol kg"^(-1)=2.79m`