According to the equation, the ratio of [tex]HC\ell[/tex] to [tex]C\ell_2[/tex] is [tex]4:1[/tex]. Then:
[tex]\dfrac{n_{HC\ell}}{n_{C\ell_2}}=\dfrac{4}{1}\Longrightarrow\dfrac{0.268}{n_{C\ell_2}}=\dfrac{4}{1}\Longrightarrow n_{C\ell_2}=\dfrac{0.268}{4}\iff n_{C\ell_2}=0.067~mol[/tex]
Now we can calculate the mass of [tex]C\ell_2[/tex] formed.
[tex]m_{C\ell_2}=n_{C\ell_2}\cdot MM_{C\ell_2}\Longrightarrow m_{C\ell_2}=0.067\cdot(2\cdot35.5)\Longrightarrow\\\\
m_{C\ell_2}=0.067\cdot71\Longrightarrow\boxed{m_{C\ell_2}=4.757~g}[/tex]
