The ones that are chipped will be extracted much faster than the ones that are broken. Depending on teh severity of the crack, the wisdom teeth could take 45 minutes to be extracted. The chipped molars won't take nearly that long. I suggest that you get knocked out, i understand that wasn't your question, but an anxiety problem plus that long in the chair equals that you should get knocked out.
It would probably help to buy some tylenol in case you're out, as your gums will be swelled and in a wee bit of pain after the extraction. Hope that helped.