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# The density of $2M$ solution of sodium chloride (NaCl) $1.13\; g\; mol/litre$. Calculate molality of the solution. $M= 2$ mol per litre.

Mass of Nacl in 1 litre solution $=2 \times 58.5 =117.0\;g$
Mass of 1 litre solution $=1000 \times 1.13 =1130\;g$
Mass of water in solution $=1130\;g-117.0\;g=1013\;g$
$\qquad= 2\;mol /1.013\;kg$
$\qquad= 1.9743\;Molality$