If $100 \ g$ of a $0.2 \ m$ aqueous solution is diluted by adding $200 \ g$ of water,what will be the molality of the resulting solution?

$A$ solution of $x \ g$ of an optically active substance dissolved in $10 \ mL$ of alcohol is placed in a polarimeter tube of $10 \ cm$ length. The observed rotation is $+2^o$. If the specific rotation is $+16^o$,what is the value of $x$ in $g$?

What mass of ethanol in $g$ must be added to $1.0 \, kg$ of water to have a mole fraction of ethanol equal to $0.2$?

What is the molarity of a $1 \ L$ solution of $93\% \ (w/v)$ $H_2SO_4$ (in $M$)? The density of the solution is $1.84 \ g/mL$.

$25.3 \ g$ of sodium carbonate,$Na_2CO_3$ is dissolved in enough water to make $250 \ mL$ of solution. If sodium carbonate dissociates completely,the molar concentration of sodium ions,$Na^{+}$,and carbonate ions,$CO_3^{2-}$,are respectively:
(Molar mass of $Na_2CO_3 = 106 \ g \ mol^{-1}$)

Explain molarity and molality in short.