im pretty sure, regardless of your hardware it will be able to run ubuntu.
as for creating a bootable USB on mac... thats easier said than done.
Follow
This Guide
you will need to work almost entirely from the command prompt, so you might want to copy/paste the commands.
dont bother with unetbootin, it will copy everything to the drive but it wont be bootable. Believe me, i have tried, a lot.
once you have the USB stick, put it into the rear USB port, power on your computer, press f11 (I think for ASRock boards) to open the boot menu, and select your USB drive. then just follow the prompts.
The guide does mention ubuntu 14, but it is completely the same for recent versions too. I did one just last week for an old netbook from my macbook air. so longas you follow each command to the letter, you should be good.