The first step we have to follow is to find the molecular mass of CaCl2.
[tex]\begin{gathered} Ca=40\times1=40 \\ Cl_2=35.45\times2=70.9 \\ CaCl_2=40+70.9=110.9 \end{gathered}[/tex]Finally divide the mass of Cl2 by the mass of CaCl2 and multiply this product times 100:
[tex]\frac{70.9}{110.9}\cdot100=63.93[/tex]It means that the correct answer is 64%.
