Charcoal is mixed in $500 \ mL$ of $0.5 \ M$ acetic acid solution. After some time,the concentration of the solution becomes $0.3 \ M$. Find the total number of molecules adsorbed on the surface of the charcoal.

• A
  $6 \times 10^{23} \text{ molecules}$
• B
  $6 \times 10^{22} \text{ molecules}$
• C
  $6 \times 10^{24} \text{ molecules}$
• D
  $6 \times 10^{21} \text{ molecules}$