divide what voltage?
The supply voltage.
To give a signal ground.
Op amps require a positive and negative power supply. You haven't got one, so to trick it you make a false signal ground at +2.5V with a potential divider and use some capacitors to lower the impedance.
oh sorry it was 741.
Look at the data sheet, it won't work with just a 5V supply. The data sheet says it needs a +/- 12V supply. That's 24V in total. You are only giving it +/- 2.5V.
An op amp has a gain of several thousand, when you say no input do you mean the two inputs connected together, that is the only way to have no input on an op amp.