You don't want to chisel this out.  Make parallel cuts using a circular saw and concrete cutting blade, then break it out with your chisel.  I have this done by the general contractors crew on jobs all the time.  They don't use special concrete saws for small jobs like this, just a standard 7" circular saw with diamond blade and use a water bottle to wet the cut a bit and keep the dust down if this is an issue.

Once you have the cuts made, the concrete will break out fairly easily.  Lay in your conduit and then fill back in with concrete mix.