Answer
$1.80\times10^{2}\frac{g\ Cl}{1\ year}$
Work Step by Step
If the car emits $25g\ CF_{2}Cl_{2}$ a month then it will emmit $25\times 12=300g \ CF_{2}Cl_{2}$ in a year. Divide this number by the molar mass of $CF_{2}Cl_{2}$ to get the number of moles of $CF_{2}Cl_{2}$. Then multiply by 2 because there are 2 $Cl$ for every mole of $CF_{2}Cl_{2}$. Finally, multiply by the molar mass of $Cl$.
$300g\ CF_{2}Cl_{2}\times\frac{1 mol\ CF_{2}Cl_{2}}{120.91g\ CF_{2}Cl_{2}}\times2\times\frac{35.45g\ Cl}{1mol\ Cl}=\frac{1.80\times10^{2}g\ Cl}{1\ year}$
