If the density of lake water is 1.25 g `mL^(-1)` and it contains 92 g of `Na^(+)` ions per kg of water, calculate the molality of `Na^(+)` ions in the lake.

Options

A. 2 m
B. 4m
C. 8 m
D. 10 m

Answer

B

Explanation

Given, Density `=1.25" g "mL^(-1)`
`"Number of moles of Na"^(+) ions =(92)/(23)mol`
`"Molality of Na" ^(+) ions ("m")=("Number of moles of" Na^(+)ions)/("Mass of water (in kg)")`
`=((92g)//(23" g "mol^(-1)))/(1kg)=4mol " kg"^(-1)or4 " m "`