$0.1 \ mol$ of $NaCl$ is dissolved in $100 \ g$ of water. The mole fraction of $NaCl$ is

$A$ solution containing $200 \ mL$ of $0.5 \ M$ $KCl$ is mixed with $50 \ mL$ of $19 \% \ w/v$ $MgCl_2$ and the resulting solution is diluted $8$ times. What is the molarity of the chloride ion in the final solution?

$A$ sample of drinking water is severely contaminated with chloroform $(CHCl_3)$. $CHCl_3$ is considered carcinogenic in nature. The level of contamination was $15 \ ppm$ (by mass).
$(i)$ Express this in percent by mass.
$(ii)$ Determine the molality of chloroform in the water sample.

Calculate the amount of benzoic acid $(C_{6}H_{5}COOH)$ required for preparing $250 \ mL$ of $0.15 \ M$ solution in methanol.

$25 \ mL$ of $3.0 \ M \ HNO_3$ are mixed with $75 \ mL$ of $4.0 \ M \ HNO_3$. If the volumes are additive,the molarity of the final mixture would be ......... $M$.

Calculate the molarity if $30 \, mL$ of $0.5 \, M$ $H_2SO_4$ is diluted to $500 \, mL$. (in $, M$)