Answer
$59.0kg\ \frac{Cl}{year}$
Work Step by Step
If the car emits $12kg\ CHF_{2}Cl$ a month then it will emit $12×12=144kg\ CHF_{2}Cl$ or $144,000g\ CHF_{2}Cl$ in a year. Divide this number by the molar mass of $CHF_{2}Cl$ to get the number of moles of $CHF_{2}Cl$. The multiply by the molar mass of Cl to convert to grams. Divide by 1000 to convert back to kilograms.
$144,000g\ CHF_{2}Cl\times\frac{1 mol\ CHF_{2}Cl}{86.47g\ CHF_{2}Cl}\times\frac{35.45g\ Cl}{1mol\ Cl}\times\frac{1}{1000}=59.0kg\ Cl$
