[tex]\qquad\qquad\huge\underline{{\sf Answer}}[/tex]
Here we go ~
1 mole of [tex] \sf{ COCl_2} [/tex] has 6.022 × 10²³ molecules of the given compound.
So, 0.78 mole of [tex] \sf{COCl_2} [/tex] will have ~
[tex]\qquad \sf \dashrightarrow \: 0.78 \times 6.022 \times 10 {}^{23} [/tex]
[tex]\qquad \sf \dashrightarrow \: \approx4.7 \times 10 {}^{23} \: \: \: molecules[/tex]
