It may be possible as the notebook was also available with an i5 430M CPU, we will need the MB details in order to try and confirm this as the MB may not have been the same for both spec notebooks, download and run Speccy and post the resultant url for us please, details here
Please be aware that if the i5 CPU is compatible with the present MB you will need to upgrade the BIOS before removing the i3 CPU so that the new i5 CPU is recognised on first boot, updating/flashing the BIOS has the potential to render a computer useless if something goes wrong during the process such as the loss of power to the computer for whatever reason (power cut etc) for such a minimal gain (i3 2133 MHz Vs the i5 stock 2267 MHz) do you feel that the risk, cost or time and inconvenience is worth it.
The Acer Aspire 5740G notebook that is shipped with an i5 CPU here
The present i3 specifications here
The proposed i5 specifications here
Both CPUs are the same socket type etc.