What is the molality of a solution made made by dissolving 2 moles of NaOH in 6 kg of water?
More specifically, molality is defined as the number of moles of solute divided by the mass of the solvent expressed in kilograms.
#color(blue)("molality" = "moles of solute"/"kg of solvent")#
In your case, sodium hydroxide,
The problem provides you with all the information you need to find the solution's molality, so just plug in your values to get
#color(blue)(b = n_"solute"/m_"solvent")#
#b = "2 moles"/"6 kg" = 0.333color(white)(a) overbrace("mol kg"^(-1))^(color(purple)("molal")) = "0.333 molal"#
Rounded to one significant figure, the answer will be
#b = color(green)("0.3 molal")#
Alternatively, you can say that because sodium hydroxide is a strong base that dissociates completely in aqueous solution, you will have a solution that is