solve briefly

A 2 L solution is prepared by dissolving 0.4 g of NaCl in water at 277 K.

Assuming the density of solution to be 1 g/cm³, The concentration of NaCl, expressed in ppm in the resultant solution is

Mass of solute (NaCl) = 0.4 g
Volume of solution = 2L = 2000 ml
Mass of solution = density $\times$ volume
                       = 1g/ml$\times$2000 ml
                       = 2000 g

Concentration of solute in ppm (parts per million) is given as = $\frac{\mathrm{mass} \mathrm{of} \mathrm{solute}}{\mathrm{mass} \mathrm{of} \mathrm{solution} }\times {10}^6$
 
                                                                                         = $\frac{0.4 \mathrm{g}}{2000 \mathrm{g}}\times {10}^6$

                                                                                        = 200 ppm

​Thus concentration of NaCl is 200 ppm.