Karabiner mapping to make the function keys on Razer Keyboard match the labels on the keyboard
Download and install Karabiner, then go to Misc & Uninstall, Open private.xml, and paste the contents of private.xml into your file and save it. Go to the Change Key tab in Karabiner, hit Reload XML, and check the options:
- Volume to Razer Mappings
- Play Buttons to Razer Mappings
- Brightness Buttons to F11/F12
Follow the instructions here.