Molality of 1 M `NaNO_3` solution (Density of solution is `1.25 g Ml^(-1)`and mol. wt. of `NaNO_3 = 85 g mol^(-1)` ) is

Options

A. 1.286 m
B. 4.44 m
C. 0.858 m
D. none of these.

Answer

C

Explanation

`rho=1.25 g mL^(-1), M_(NaNO_3) = 85 g mol^(-1), Molarity = 1`
`M 1/m =rho/M (M_(NaNO_3))/1000 implies 1/m = (1.25)/1 - 85/1000 = 1.25 -0.085 = 1.165 " in " = 0.858 2`.