What type of solution is sea water?

$A$ $2.0 \, M$ solution is obtained when $0.5 \, mole$ of solute is dissolved in:

What is the mole fraction of the solute in $2.5 \ m$ aqueous solution?

$3.1 \ g$ of a compound,'$X$' (molar mass $= 62 \ g \ mol^{-1}$) is dissolved in $19.5 \ g$ of other compound,$Y$ (molar mass $= 78 \ g \ mol^{-1}$). The ratio of mole fractions of $X$ and $Y$ in the solution is

The molality of the solution prepared by dissolving $125 \ mL$ of pure methanol $(d = 0.8 \ g \ mL^{-1})$ in $375 \ g$ of ethanol is

The volume of water added to $500 \ mL$ of $0.5 \ M \ NaOH$ solution so that its strength becomes $10 \ mg \ mL^{-1}$ will be .......... $mL$.