Final answer:
The voltage across C3, which is in parallel with C2, is the same as V2 and is calculated to be 8.0V. The charge on C3 can be found using the formula Q3 = C3 * V3, where V3 is confirmed to be 8.0V.
Step-by-step explanation:
To calculate the voltage across C3, we need to understand that the voltage across capacitors connected in parallel is the same. From the information provided, C2 and C3 form a parallel combination. Therefore, V2 = V3. The question mentions that V2 is given by 12.0V subtracting 4.0V, which is 8.0V, thus V3 is also 8.0V.
The total charge on C3 can be calculated using Q = CV, which is given as Q3 = C3 * V3. Since we know V3 is 8.0V and the previous provided information or the specific value for C3 would allow us to find Q3, which is the charge on capacitor 3. Finally, with Q3 and the capacitance C3 known, we can confirm V3 = Q3 / C3.