The molality of a urea solution in which ` 0.0100 g ` of urea, ` [(NH_(2))_(2)CO] ` is added to ` 0.3000 dm^(3) `of water at STP is

Options

A. (a)`5.55xx10^(-4) M`
B. (b)33.3 M
C. (c )`3.33xx10^(-2) M`
D. (d)0.555 M

Answer

A

Explanation

`"Molality" = ("moles of the solute")/("mass of the solvent in kg")`
Moles of urea `(n_("urea"))= (0.0100 g)/(60 "g mol"^(-1))`
Mass of `1000 "mL o solution" = "volume" xx"density"`
`=300 mLxx(1 g)/(mL) [ :' 1 dm^(3)=1000 mL]`
`=300 g`
Mass of solvent `=300 g-0.0100 g`
`=299.9 g= 0.2999 kg`
`"Molality"=0.0100/(60xx0.2999)=5.55xx10^(-4) "mol kg"^(-1)`