Question & Answer: A concentrated sodium hydroxide is 50.5% NaOH by mass (100% *mass of solute/mass of…..

A concentrated sodium hydroxide is 50.5% NaOH by mass (100% *mass of solute/mass of solution) and has a density of 1.53 g/mL at 25 degrees celcius. what is the molality of NaOH?

Expert Answer

Answer

sodium hydroxide is 50.5% NaOH by mass means 50.5 g of NaOH in 100 g solution

weight of solvent = weight of solution -weight of solute i.e. $Rightarrow$ 100-50.5 = 49.5

Molality = wt. of solute*1000/ molecular weight* weight of solvent

$Rightarrow$ 50.5*1000/40*49.5 = 2.55 moles/Kg

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