# What is the molality of a 1M NaOH solution?

Jun 23, 2018

The molal concentration is 1 mol/kg.

#### Explanation:

Assume you have 1 L of the solution. Then you have 1 mol (40 g) of $\text{NaOH}$.

The density of the solution is 1.04 g/mL.

$\text{Mass of solution" = 1000 color(red)(cancel(color(black)("mL solution"))) × "1.04 g solution"/(1 color(red)(cancel(color(black)("mL solution")))) = "1040 g solution}$

$\text{Mass of water" = "(1040 - 40) g = 1000 g = 1.0 kg}$

$b = \text{moles of solute"/"kilograms of solvent" = "1 mol"/"1.0 kg" = "1 mol/kg}$

The molal concentration is 1 mol/kg.