When $7.1 \ g$ of $Na_2SO_4$ (molecular mass $142$) dissolves in $100 \ mL$ of $H_2O$,the molarity of the solution is $.........$ $M$.

$250 \, mL$ of a sodium carbonate solution contains $2.65 \, g$ of $Na_2CO_3$. If $10 \, mL$ of this solution is diluted to $1 \, L$,what is the concentration of the resultant solution? (Molecular weight of $Na_2CO_3 = 106$)

$V_1 \ \text{c.c.}$ of a solution having molarity $M_1$ is diluted to have molarity $M_2$. The volume of water required to be added will be $:-$

Calculate the mass percentage of aspirin $(C_{9}H_{8}O_{4})$ in acetonitrile $(CH_{3}CN)$ when $6.5 \ g$ of $C_{9}H_{8}O_{4}$ is dissolved in $450 \ g$ of $CH_{3}CN$.

Two solutions of a substance are mixed as follows: $480 \ mL$ of $1.5 \ M$ first solution + $520 \ mL$ of $1.2 \ M$ second solution. The molarity of the final solution will be ............. $M$.

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