Almost certainly not. The iMac G5 Rev A is the most finicky G5 machine made, and the Kingston ValueRAM (KVR-series) are widely reported as not being Mac compatible (this obviously varies by model)
The only Kingston RAM that is guaranteed compatible with your machine is the KTA-IMAC400/512 and KTA-IMAC400/1G
Look for a reputable seller who tests and guarantees compatibility with your model Mac, offers a lifetime warranty and a no cost (no restocking charge) return if it doesn't work.