In the following circuit C 1 = 12   μF , C 2 = C 3 = 4   μF and C 4 = C 5 = 2  …

From circuit given,

Capacitors $C_2, C_3, C_4$ and $C_5$ are in parallel connection with constant potential difference as $2 \mathrm{V}$.

Now, charge stored in $C_3$ is $Q_3=2\times 4 \mathrm{\mu C}$$=8 \mathrm{\mu C}$.