A water treatment plant uses sodium chloride ($NaCl$) to regenerate ion-exchange water softeners. If $58.5 \, \text{kg}$ of $NaCl$ is dissolved in enough water to make $2000 \, \text{L}$ of brine solution, what is the molarity of the solution? (Molar mass of $NaCl = 58.44 \, \text{g/mol}$).

A $500 \, \text{g}$ sample of groundwater is found to contain $0.015 \, \text{g}$ of dissolved lead ($Pb^{2+}$). Calculate the concentration of lead in mass percent and parts per million (ppm).

The Henry's law constant for oxygen gas ($O_2$) in water at $25^\circ\text{C}$ is $1.3 \times 10^{-3} \, \text{M/atm}$. If the partial pressure of oxygen in the atmosphere is $0.21 \, \text{atm}$, calculate the concentration of dissolved oxygen in an aeration tank at equilibrium.

To prevent ice formation, municipalities spread Calcium Chloride ($CaCl_2$) on roads. Calculate the freezing point of a solution made by dissolving $500 \, \text{g}$ of $CaCl_2$ in $2.00 \, \text{kg}$ of water. (Molar mass $CaCl_2 = 110.98 \, \text{g/mol}$; $K_f$ for water $= 1.86^\circ\text{C/m}$; assume ideal dissociation).