what is the voltage across the second capacitor?
In series combination, the potential across any capacitor is inversly proportional to its capacity If the voltage across the first capacitor (the one with capacitance C) is V', then V'=Q /C The voltage across second capacitor =Q/2C =(1/2)Q/C=V'/2 The voltage across third capacitor =Q/3C =(1/3)Q/C=V'/3