That made me laugh.
Chlorine is a gas and will get out of the water by itself in 24 hours.
But the lemons,you have to squeeze them and mix the juice with the water or else they will not do nothing.You also added too manny lemons most likely ( this depends on the buffer that its the water and you cant know how much it is until you measure the ph and add acid little by little).
Rain water is verry ,,clean,, and if it has high Ph ,lets assume 8,you would only need a few drops of acid to lower it to 6 because it has verry little carbonate in it( carbonate= it is called buffer).
But if your tap water has a ph of 7,5 but a blot of buffer in it then you will need the juice of a whole lemon to lower it to 6 for that bucket .
Essential to know: the more buffer( carbonate) is in the water,the more acid you need to lower the ph.
Lemons are also a verry expensive way to lower the ph of the water.
When you hear people that say they use citric acid to lower the ph of the water,they use synthetic citric acid,the soo called lemmon salt ( wich is not a salt but an organic acid made synthetical and in the form of crystals like table sugar).
Get a ph meter with a glass probe ( not the junk ones advertised to be usef for plants) measure the ph and use vinegar because its better than lemons and also cheaper.
Adjust acordingly after.
Best solution is to use sulphur but takes long time to lower the ph that way.
Another solution for the water,the best solution by now,is to use wood vinnegar or liquid smoke as its called or pyroligneous acid wich consists of humic and fulvic acids.It usually costs @ 5-10 dollars a litter and lasts a long way but its verry hard to find in western countryes,mainly asians are using it.