The unit of molality is

In $500 \ mL$ of $0.2 \ M \ NaCl$ solution,$1500 \ mL$ of $0.4 \ M \ MgCl_2$ solution is mixed. The only incorrect final concentration of ion is (assume volume to be additive)

If the density of a $5 \ M$ solution of $KCl$ is $1.26 \ g \ mL^{-1}$,then find the molality of the solution. (molecular mass of $KCl = 74.55 \ g \ mol^{-1}$) (in $m$)

How many grams of $NaOH$ must be dissolved in $500 \, g$ of solution to obtain a $10 \% \, w/w$ concentration?

What is the mass ratio of ethylene glycol $(C_2H_6O_2, \text{molar mass} = 62 g/mol)$ required for making $500 g$ of $0.25 m$ aqueous solution and $250 mL$ of $0.25 M$ aqueous solution?

Find out the molality of a solution prepared by dissolving $2.89 \ g$ of $NaCl$ in $0.159 \ L$ of water. The density of water is $1.00 \ g / mL$. (in $m$)