The molality of a urea solution in which 0.0100 g of urea, [(NH2)2CO] is added to 0.3000 dm3 of water at STP is ?

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Answer 1 · 2018-04-10T15:38:54

#5.57 × 10^-4\ "m"#

Molar mass of urea #"= 60.06 g/mol"#

Moles of #"0.0100 g"# urea is

#"n" = "0.0100 g"/"60.06 g/mol" = 1.67 × 10^-4\ "mol"#

Mass = Volume × Density

Density of water is #10^3\ "g/dm"^3#

Mass of water #= 0.3000 cancel("dm"^3) × 10^3\ "g"/cancel("dm"^3) = "300.0 g" = "0.3 kg"#

#"Molality" = "Moles of solute"/"Mass of solvent (in kg)"#

#"Molality" = (1.67 × 10^-4\ "mol")/"0.3 kg" = color(blue)(5.57 × 10^-4\ "m")#