A$.$ Unit Conversion Assuming that all concentrations are in aqueous solution $($density $=1\mathrm{.}0$ g$/$mL$),$ answer the following.

$1.2\mathrm{.}410-3$ ng$/$L of NaCl $=??$ mg$/$kg

$2.6\mathrm{.}0103$ g$/$L of NaCl $=??$ ng$/$mL

$3.0\mathrm{.}40$ x $10-3$ ng$/$L $=\_\_\_\_\_\_$g$/$mL

$4.0\mathrm{.}80$ x $10-2$ ppm $=\_\_\_\_\_\_\_\_\_$ g$/$L

$5.0\mathrm{.}50$ mol$/$L of NaCl $(58\mathrm{.}5$ g$/$mol$)=\_\_\_\_\_\_\_\_$g$/$mL

$6.$ Find the concentration of Ca$2+(40$ g$/$mole$)$ expressed as ppm for a solution containing $0\mathrm{.}020$ M of CaCO$3(100$ g$/$mole$)$

B$.$ Preparation of Standard Solution from Stock Solution.

$7.$ Having $5\mathrm{.}0$ M of stock HCl solution, what is the initial volume of this solution needed to prepare $25\mathrm{.}0$ mL of $2\mathrm{.}0$ M HCl$?$

$8.8\mathrm{.}0$ mL of stock solution is transferred into $50\mathrm{.}0$ mL flask and diluted into the mark. If the concentration of the prepared $50\mathrm{.}0$ mL solution is $0\mathrm{.}20$ M$,$ what is the concentration of stock solution?